29.10.2020

Find sec A and cot B exactly if a = 8 and b = 7.

. 4

Faq

Mathematics
Step-by-step answer
P Answered by Master

sec A= 1.01 and cot B =8.25

Step-by-step explanation:

Given :

sec A and cotB if a =8 and b=7

Now,

=sec A=\frac{1}{cos A} \\\\\frac{1}{cos 8} \\\\\frac{1}{0.99} \\1.01

and

cot B=\frac{cosB}{sin B} \\cotB=\frac{cos 7}{sin7} \\cot B =\frac{0.99}{0.12} \\cot B =8.25

Therefore, answer will be sec A= 1.01 and cot B =8.25

Mathematics
Step-by-step answer
P Answered by Specialist

1. The given triangle ABC, has a right angle at C, BC=11, and B=30\degree

\tan 30\degree=\frac{AC}{11}

AC=11\tan 30\degree

AC=\frac{11\sqrt{3}}{3}

Ans: A

2. The reference angle is the angle the terminal side makes with x-axis.

-\frac{33\pi}{8}=-4\frac{\pi}{8}

This implies that, -\frac{33\pi}{8} has a reference angle of \frac{\pi}{8}.

Ans: C

3. Let x be the shortest distance the ramp can span.

From the diagram; \tan (4.76\degree)=\frac{2.5}{x}

\implies x=\frac{2.5}{\tan (4.76\degree)}

\implies x=30.0ft

Ans:B

4. Use the Pythagorean identity: 1+\tan ^2 \theta=\sec^2 \theta.

If \cot \theta=-\frac{1}{2},then  \tan \theta=-2

\implies 1+2^2=\sec^2 \theta

\implies \sec^2 \theta=5

\implies \sec \theta=-\sqrt{5}, In QII, the secant ratio is negative.

Ans:C

5. We have \sin \frac{2\pi}{3}=\frac{\sqrt{3} }{2}

\cos \frac{\pi}{6}=\frac{\sqrt{3} }{2}

\cos \frac{\pi}{3}=\frac{1}{2}

\sin \frac{5\pi}{3}=-\frac{\sqrt{3} }{2}

\cos \frac{7\pi}{6}=-\frac{\sqrt{3} }{2}

\cos \frac{11\pi}{6}=\frac{\sqrt{3} }{2}

Ans:A and D

6.  The given function that is equivalent to f(x)=\sin x is f(x)=\cos (-x+\frac{\pi}{2}).

When we reflect the graph of  f(x)=\cos (x)  in the y-axis and shift it to the left by  \frac{\pi}{2} units, it coincides with graph of f(x)=\sin x.

Ans:C

7. The function y=\tan x is a one-to-one function on the interval [-\frac{\pi}{2},\frac{\pi}{2}]

When we restrict the domain of  y=\tan x on [-\frac{\pi}{2},\frac{\pi}{2}] it becomes an invertible function.

Ans: C

8. The given function is y=3\sin(4x-\pi)

The horizontal shift is given by \frac{C}{B}=\frac{\pi}{4}

The direction of the shift is to the right.

Ans:D

9.  \cos(-75\degree)=\cos(75\degree) by the symmetric property of even functions.

\cos(75\degree)=\cos(45\degree+30\degree)

\cos(75\degree)=\cos(45\degree) \cos30\degree-\sin(45\degree) \sin30\degree

\cos(75\degree)=\frac{\sqrt{2} }{2} \times \frac{\sqrt{3} }{2} -\frac{\sqrt{2} }{2} \times \frac{1}{2}

\cos(75\degree)=\frac{\sqrt{6}-\sqrt{2}}{4}

Ans: B

10. Recall the cosine rule: a^2=b^2+c^2-2bc\cos A

Let the angle measure opposite to the longest side be A, then a=19,b=17, and c=15.

\Rightarrow 19^2=17^2+15^2-2(17)(15)\cos A

\implies -153=-510\cos A

\implies \cos A=0.3

\implies A=\cos^{-1}(0.3)=73\degree

Ans:B

11.  We want to solve 2\sin(2x)\cos(x)-\sin(2x)=0 on the interval;

[-\frac{\pi}{2},\frac{\pi}{2}]

Factor:  \sin2(x)[2\cos(x)-1)=0

Either \sin(2x)=0 \implies x=0\frac{\pi}{2}

Or [2\cos x-1=0 This means that x=\frac{\pi}{3},-\frac{\pi}{3}

Therefore required solution is x=-\frac{\pi}{3},0,\frac{\pi}{3},\frac{\pi}{2}

Ans:D

12. Use the relation:r=\sqrt{x^2+y^2} and \theta=\tan^{-1}(\frac{y}{x})=

The given rectangular coordinate is (1,-2)

This implies that:r=\sqrt{1^2+(-2)^2}=\sqrt{5}

\theta=\tan^{-1}(\frac{-2}{1})= This means  \theta=116.6 or \theta=296.6

The polar forms are: -\sqrt{5},116.6 and \sqrt{5},296.6

Ans: B and C

13.  The polar equation that represents an ellipse is

r=\frac{2}{2-\sin \theta}.

When written in standard form; r=\frac{1}{1-0.5\sin \theta}.

The eccentricity is 0.5\:.

Therefore the r=\frac{2}{2-\sin \theta} is an ellipse.

Ans: B

14. The DeMoivre’s Theorem states that;

(\cos \theta+i\sin \theta)^n=\cos n\theta+i\sin n\theta

This implies that:

[2(\cos \frac{\pi}{9}+i\sin \frac{\pi}{9})]^3=2^3\cos 3\times \frac{\pi}{9}+i\sin 3\times \frac{\pi}{9})

[2(\cos \frac{\pi}{9}+i\sin \frac{\pi}{9})]^3=8(frac{2}{2})+i8(\frac{\sqrt{3}}{2})=4+4\sqrt{3}i

Ans: A

15. Let the initial point be (x,y), Then |v|=\sqrt{(-2-x)^2+(4-y)^2}.

If x=-8, and y=-4.

Then, |v|=\sqrt{(-2--8)^2+(4--4)^2}.

|v|=\sqrt{(-6)^2+(8)^2}=\sqrt{100}=10.

Ans: B

16. We find the dot product to see if it is zero.

u\bullet v=-6(7)+4(10)=-2

Since the dot product is not zero the vectors are not orthogonal

\theta=\cos ^{-1}(\frac{u\bullet v}{|u||v|})

\theta=\cos ^{-1}(-\frac{2}{2\sqrt{13}\times \sqrt{1149} }) =91.3\degree

Ans:B

17. Given v=5i+4j, w=2i-3j.

u=v+w

Add corresponding components

This implies u=(5i+4j)+(2i-3j)

u=(5i+2i+4j-3j)

u=7i+j

Ans:B

See attachment.


1. in abc, c is a right angle and bc= 11. if the measure of angle b= 30degrees, find ac. a) (11sqrt3
1. in abc, c is a right angle and bc= 11. if the measure of angle b= 30degrees, find ac. a) (11sqrt3
Mathematics
Step-by-step answer
P Answered by PhD
We know that
sec (theta)=1/cos (theta)

cot (theta) = -2
cot (theta)=cos (theta)/sin (theta)
cos (theta)/sin (theta)=-2> squaring> cos² (theta)/sin² (theta)=4
remember that
sin²(theta)+cos²(theta)=1
sin² (theta)=1-cos² (theta)
substitute
 cos² (theta)/[1-cos² (theta)]=4
cos² (theta)=4*[1-cos² (theta)]> cos² (theta)+4 cos² (theta)=4
5*cos² (theta)=4> cos² (theta)=4/5> cos (theta)=2/√5
cos (theta)=(2√5)/5> is positive  (IV quadrant)
sec (theta)=1/cos (theta)> √5/2

the answer is
sec (theta)=√5/2
Mathematics
Step-by-step answer
P Answered by PhD
We know that
sec (theta)=1/cos (theta)

cot (theta) = -2
cot (theta)=cos (theta)/sin (theta)
cos (theta)/sin (theta)=-2> squaring> cos² (theta)/sin² (theta)=4
remember that
sin²(theta)+cos²(theta)=1
sin² (theta)=1-cos² (theta)
substitute
 cos² (theta)/[1-cos² (theta)]=4
cos² (theta)=4*[1-cos² (theta)]> cos² (theta)+4 cos² (theta)=4
5*cos² (theta)=4> cos² (theta)=4/5> cos (theta)=2/√5
cos (theta)=(2√5)/5> is positive  (IV quadrant)
sec (theta)=1/cos (theta)> √5/2

the answer is
sec (theta)=√5/2
Mathematics
Step-by-step answer
P Answered by PhD

1. C. 1 + cot²θ = cos²θ

D. 1 - sec²θ = tan²θ

2. D. 0

3. C. Any square is a rectangle

4. C. Parallelogram

5. B. 30 m

6. A. cos(-890°) is Negative

Sin(-890°) is negative

7. A. 100·√3 m

8. \left (\dfrac{-8}{3} , \dfrac{1}{3}  \right )

9. First option, A. 68 unit

10. A. 150

Step-by-step explanation:

1. C. 1 + cot²θ = cos²θ

The correct identity is given as follows;

1 + cot²θ = csc²θ

Also

D. 1 - sec²θ = tan²θ

The correct identity is given as follows;

1 - sec²θ = -tan²θ

2. cot(-8550)

We convert -8550 to degrees by dividing by 360 and multiplying the remaining fraction by 360 as follows;

\dfrac{-8550}{360} = -23\dfrac{3}{4}

Therefore, -8550 ≅ -3/4×360 = -270

-270 ≅ 360 - 270 = 90°

Therefore, cot(-8550) = cot(90) = 1/(tan(90)) = 1/∞ = 0

Therefore, the correct option is the option D. 0

3. The correct option is any square is a rectangle as a square (a rectangle with all sides equal) is a subset of the set of rectangles

The correct option is C. Any square is a rectangle.

4. Where the diagonals bisect each other, we have a shape where the two opposite triangle areas across the bisector are equal

Therefore, the quadrilateral is necessarily a C. Parallelogram

5. Where by the angle of depression = 45°

Therefore, the angle of elevation = 45° (Alternate angles)

The height of the building = 30 m

Therefore, tan(45°) = (30 m)/(Distance of point A from the building) = 1

∴ The distance of point A from the building = 30 m

The correct option is therefore;

B. 30 m

6. A. -890° = 190° which is in the second quadrant

Therefore, cos(190°) = Negative

B. -1200° = -120° = 240 which is in the third quadrant

Hence, tan(-1200) = tan(240) is positive

C. Sin(1200) = Sin(120) which is in the second quadrant

Hence, sin(1200) is positive

D. Sin(-890°) = Sin(190°) which is in the third quadrant

Hence, sin(-890) is negative

7. The distance from the wall where the measurement is taken = 100/(tan(30)) = 100·√3 = 173.21 m

The total height of the antenna from the ground = 173.21 × tan(45) = 100·√3 m

The total height of the antenna from the ground is 100·√3 m

The correct option is therefore;

A. 100·√3 m

8. The coordinates of the point of intersection of the medians is given by the relation;

Centroid = \left (\dfrac{x_{1}+x_{2}+x_{3}}{3} , \dfrac{y_{1}+y_{2}+y_{3}}{3}  \right )

Where:

x₁, y₁ x₂, y₂, x₃, y₃ are the coordinates of the vertices

We therefore have;

Median \, point= \left (\dfrac{(-2) +(-2)+(-4)}{3} , \dfrac{3+(-7)+5}{3}  \right ) = \left (\dfrac{-8}{3} , \dfrac{1}{3}  \right )

9. The perimeter of the rhombus = 4×√(First diagonal)/2)

The \, perimeter \, of \, the \, rhombus = 4\times \sqrt{\left (\dfrac{First \, diameter}{2}  \right )^{2}+ \left (\dfrac{Second \, diameter}{2}  \right )^{2}}

= 4\times \sqrt{\left (\dfrac{16}{2}  \right )^{2}+ \left (\dfrac{30}{2}  \right )^{2}} = 68 \ unit

The correct option is A. 68 unit

10. The exterior angle of a regular polygon > 180°, therefore, the correct option is A. 150

Mathematics
Step-by-step answer
P Answered by PhD

1. C. 1 + cot²θ = cos²θ

D. 1 - sec²θ = tan²θ

2. D. 0

3. C. Any square is a rectangle

4. C. Parallelogram

5. B. 30 m

6. A. cos(-890°) is Negative

Sin(-890°) is negative

7. A. 100·√3 m

8. \left (\dfrac{-8}{3} , \dfrac{1}{3}  \right )

9. First option, A. 68 unit

10. A. 150

Step-by-step explanation:

1. C. 1 + cot²θ = cos²θ

The correct identity is given as follows;

1 + cot²θ = csc²θ

Also

D. 1 - sec²θ = tan²θ

The correct identity is given as follows;

1 - sec²θ = -tan²θ

2. cot(-8550)

We convert -8550 to degrees by dividing by 360 and multiplying the remaining fraction by 360 as follows;

\dfrac{-8550}{360} = -23\dfrac{3}{4}

Therefore, -8550 ≅ -3/4×360 = -270

-270 ≅ 360 - 270 = 90°

Therefore, cot(-8550) = cot(90) = 1/(tan(90)) = 1/∞ = 0

Therefore, the correct option is the option D. 0

3. The correct option is any square is a rectangle as a square (a rectangle with all sides equal) is a subset of the set of rectangles

The correct option is C. Any square is a rectangle.

4. Where the diagonals bisect each other, we have a shape where the two opposite triangle areas across the bisector are equal

Therefore, the quadrilateral is necessarily a C. Parallelogram

5. Where by the angle of depression = 45°

Therefore, the angle of elevation = 45° (Alternate angles)

The height of the building = 30 m

Therefore, tan(45°) = (30 m)/(Distance of point A from the building) = 1

∴ The distance of point A from the building = 30 m

The correct option is therefore;

B. 30 m

6. A. -890° = 190° which is in the second quadrant

Therefore, cos(190°) = Negative

B. -1200° = -120° = 240 which is in the third quadrant

Hence, tan(-1200) = tan(240) is positive

C. Sin(1200) = Sin(120) which is in the second quadrant

Hence, sin(1200) is positive

D. Sin(-890°) = Sin(190°) which is in the third quadrant

Hence, sin(-890) is negative

7. The distance from the wall where the measurement is taken = 100/(tan(30)) = 100·√3 = 173.21 m

The total height of the antenna from the ground = 173.21 × tan(45) = 100·√3 m

The total height of the antenna from the ground is 100·√3 m

The correct option is therefore;

A. 100·√3 m

8. The coordinates of the point of intersection of the medians is given by the relation;

Centroid = \left (\dfrac{x_{1}+x_{2}+x_{3}}{3} , \dfrac{y_{1}+y_{2}+y_{3}}{3}  \right )

Where:

x₁, y₁ x₂, y₂, x₃, y₃ are the coordinates of the vertices

We therefore have;

Median \, point= \left (\dfrac{(-2) +(-2)+(-4)}{3} , \dfrac{3+(-7)+5}{3}  \right ) = \left (\dfrac{-8}{3} , \dfrac{1}{3}  \right )

9. The perimeter of the rhombus = 4×√(First diagonal)/2)

The \, perimeter \, of \, the \, rhombus = 4\times \sqrt{\left (\dfrac{First \, diameter}{2}  \right )^{2}+ \left (\dfrac{Second \, diameter}{2}  \right )^{2}}

= 4\times \sqrt{\left (\dfrac{16}{2}  \right )^{2}+ \left (\dfrac{30}{2}  \right )^{2}} = 68 \ unit

The correct option is A. 68 unit

10. The exterior angle of a regular polygon > 180°, therefore, the correct option is A. 150

Mathematics
Step-by-step answer
P Answered by PhD

A. The exact value of sec(13π/6) = 2√3/3

B. The exact value of cot(7π/4) = -1

Step-by-step explanation:

* Lets study the four quadrants

# First quadrant the measure of all angles is between 0 and π/2

  the measure of any angle is α  

∴ All the angles are acute  

∴ All the trigonometry functions of α are positive

# Second quadrant the measure of all angles is between π/2 and π

  the measure of any angle is π - α

∴ All the angles are obtuse

∴ The value of sin(π - α) only is positive

  sin(π - α) = sin(α)  ⇒ csc(π - α) = cscα

  cos(π - α) = -cos(α)   ⇒ sec(π - α) = -sec(α)

  tan(π - α) = -tan(α)   ⇒ cot(π - α) = -cot(α)

# Third quadrant the measure of all angles is between π and 3π/2

  the measure of any angle is π + α  

∴ All the angles are reflex  

∴ The value of tan(π + α) only is positive

  sin(π + α) = -sin(α)  ⇒ csc(π + α) = -cscα

  cos(π + α) = -cos(α)   ⇒ sec(π + α) = -sec(α)

  tan(π + α) = tan(α)   ⇒ cot(π + α) = cot(α)

# Fourth quadrant the measure of all angles is between 3π/2 and 2π  

  the measure of any angle is 2π - α  

∴ All the angles are reflex

∴ The value of cos(2π - α) only is positive

  sin(2π - α) = -sin(α)  ⇒ csc(2π - α) = -cscα

  cos(2π - α) = cos(α)   ⇒ sec(2π - α) = sec(α)

  tan(2π - α) = -tan(α)   ⇒ cot(2π - α) = -cot(α)

* Now lets solve the problem

A. The measure of the angle 13π/6 = π/6 + 2π

- The means the terminal of the angle made a complete turn (2π) + π/6

∴ The angle of measure 13π/6 lies in the first quadrant

∴ sec(13π/6) = sec(π/6)

∵ sec(x) = 1/cos(x)

∵ cos(π/6) = √3/2

∴ sec(π/6) = 2/√3 ⇒ multiply up and down by √3

∴ sec(π/6) = 2/√3 × √3/√3 = 2√3/3

* The exact value of sec(13π/6) = 2√3/3

B. The measure of the angle 7π/4 = 2π - π/4

- The means the terminal of the angle lies in the fourth quadrant

∴ The angle of measure 7π/4 lies in the fourth quadrant

- In the fourth quadrant cos only is positive

∴ cot(2π - α) = -cot(α)

∴ cot(7π/4) = -cot(π/4)

∵ cot(x) = 1/tan(x)

∵ tan(π/4) = 1

∴ cot(π/4) = 1

∴ cot(7π/4) = -1

* The exact value of cot(7π/4) = -1

Mathematics
Step-by-step answer
P Answered by PhD

A. The exact value of sec(13π/6) = 2√3/3

B. The exact value of cot(7π/4) = -1

Step-by-step explanation:

* Lets study the four quadrants

# First quadrant the measure of all angles is between 0 and π/2

  the measure of any angle is α  

∴ All the angles are acute  

∴ All the trigonometry functions of α are positive

# Second quadrant the measure of all angles is between π/2 and π

  the measure of any angle is π - α

∴ All the angles are obtuse

∴ The value of sin(π - α) only is positive

  sin(π - α) = sin(α)  ⇒ csc(π - α) = cscα

  cos(π - α) = -cos(α)   ⇒ sec(π - α) = -sec(α)

  tan(π - α) = -tan(α)   ⇒ cot(π - α) = -cot(α)

# Third quadrant the measure of all angles is between π and 3π/2

  the measure of any angle is π + α  

∴ All the angles are reflex  

∴ The value of tan(π + α) only is positive

  sin(π + α) = -sin(α)  ⇒ csc(π + α) = -cscα

  cos(π + α) = -cos(α)   ⇒ sec(π + α) = -sec(α)

  tan(π + α) = tan(α)   ⇒ cot(π + α) = cot(α)

# Fourth quadrant the measure of all angles is between 3π/2 and 2π  

  the measure of any angle is 2π - α  

∴ All the angles are reflex

∴ The value of cos(2π - α) only is positive

  sin(2π - α) = -sin(α)  ⇒ csc(2π - α) = -cscα

  cos(2π - α) = cos(α)   ⇒ sec(2π - α) = sec(α)

  tan(2π - α) = -tan(α)   ⇒ cot(2π - α) = -cot(α)

* Now lets solve the problem

A. The measure of the angle 13π/6 = π/6 + 2π

- The means the terminal of the angle made a complete turn (2π) + π/6

∴ The angle of measure 13π/6 lies in the first quadrant

∴ sec(13π/6) = sec(π/6)

∵ sec(x) = 1/cos(x)

∵ cos(π/6) = √3/2

∴ sec(π/6) = 2/√3 ⇒ multiply up and down by √3

∴ sec(π/6) = 2/√3 × √3/√3 = 2√3/3

* The exact value of sec(13π/6) = 2√3/3

B. The measure of the angle 7π/4 = 2π - π/4

- The means the terminal of the angle lies in the fourth quadrant

∴ The angle of measure 7π/4 lies in the fourth quadrant

- In the fourth quadrant cos only is positive

∴ cot(2π - α) = -cot(α)

∴ cot(7π/4) = -cot(π/4)

∵ cot(x) = 1/tan(x)

∵ tan(π/4) = 1

∴ cot(π/4) = 1

∴ cot(7π/4) = -1

* The exact value of cot(7π/4) = -1

Mathematics
Step-by-step answer
P Answered by PhD
Answer: 440 grams for 1.54 is the better value
Explanation:
Take the price and divide by the number of grams
1.54 / 440 =0.0035 per gram
1.26 / 340 =0.003705882 per gram
0.0035 per gram < 0.003705882 per gram
Mathematics
Step-by-step answer
P Answered by PhD

F=ma

where F=force

m=mass

a=acceleration

Here,

F=4300

a=3.3m/s2

m=F/a

    =4300/3.3

    =1303.03kg

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