SAT II Math I : Secant, Cosecant, Cotangent

Study concepts, example questions & explanations for SAT II Math I

varsity tutors app store varsity tutors android store

Example Questions

Example Question #11 : Trigonometry

If \(\displaystyle \cot \alpha = 5\) and \(\displaystyle \sin \alpha < 0\), what is the value of \(\displaystyle \sec \alpha\)?

Possible Answers:

\(\displaystyle \frac{\sqrt{26}}{5}\)

\(\displaystyle -\frac{5}{\sqrt{26}}\)

\(\displaystyle -\frac{1}{\sqrt{26}}\)

\(\displaystyle -\frac{\sqrt{26}}{5}\)

\(\displaystyle \sqrt{26}\)

Correct answer:

\(\displaystyle -\frac{\sqrt{26}}{5}\)

Explanation:

Since cotangent is positive and sine is negative, alpha must be in quadrant III.  \(\displaystyle \cot \alpha = \frac{x}{y}\) then implies that \(\displaystyle (x,y)=(-5,-1)\) is a point on the terminal side of alpha. 

\(\displaystyle r=\sqrt{(x^2+y^2)}=\sqrt{26}\)

\(\displaystyle \sec \alpha = \frac{r}{x} = \frac{\sqrt{26}}{-5}\)

Example Question #12 : Trigonometry

If \(\displaystyle \csc \theta < 0\) and \(\displaystyle \tan \theta > 0\), then which of the following must be true about \(\displaystyle \theta\).

Possible Answers:

\(\displaystyle 0 < \theta < \frac{\pi}{2}\)

\(\displaystyle \frac{3\pi}{2} < \theta < 2\pi\)

\(\displaystyle \frac{\pi}{2} < \theta < \pi\)

\(\displaystyle -\frac{\pi}{2} < \theta < 0\)

\(\displaystyle \pi < \theta < \frac{3\pi}{2}\)

Correct answer:

\(\displaystyle \pi < \theta < \frac{3\pi}{2}\)

Explanation:

Since cosecant is negative, theta must be in quadrant III or IV. 

Since tangent is positive, it must be in quadrant I or III. 

Therefore, theta must be in quadrant III.

Using a unit circle we can see that quadrant III is when theta is between \(\displaystyle \pi\) and \(\displaystyle \frac{3\pi}{2}\).

Example Question #11 : Trigonometry

The point \(\displaystyle (12, 5)\) lies on the terminal side of an angle in standard position. Find the secant of the angle.

Possible Answers:

\(\displaystyle \frac{12}{13}\)

\(\displaystyle \frac{5}{13}\)

\(\displaystyle \frac{13}{5}\)

\(\displaystyle \frac{5}{12}\)

\(\displaystyle \frac{13}{12}\)

Correct answer:

\(\displaystyle \frac{13}{12}\)

Explanation:

Secant is defined to be the ratio of \(\displaystyle r\) to \(\displaystyle x\) where \(\displaystyle r\) is the distance from the origin. 

The Pythagoreanr Triple 5, 12, 13 helps us realize that \(\displaystyle r = 13\)

Since \(\displaystyle x = 12\), the answer is \(\displaystyle \frac{13}{12}\).

Example Question #13 : Trigonometry

Given angles \(\displaystyle x\) and \(\displaystyle y\) in quadrant I, and given,

 \(\displaystyle \sin x = \frac{3}{5}\) and \(\displaystyle \cos y = \frac {5}{13}\),

find the value of \(\displaystyle \csc (x+y)\).

Possible Answers:

\(\displaystyle \frac {65}{64}\)

\(\displaystyle \frac {99}{65}\)

\(\displaystyle \frac {65}{63}\)

\(\displaystyle \frac {65}{64}\)

\(\displaystyle \frac {63}{65}\)

Correct answer:

\(\displaystyle \frac {65}{63}\)

Explanation:

Use the following trigonometric identity to solve this problem.

\(\displaystyle \csc (x+y) = \frac {1}{\sin (x+y)} = \frac {1}{\sin x \cos y + \cos x \sin y}\)

Using the Pythagorean triple 3,4,5, it is easy to find \(\displaystyle \cos x = \frac {4}{5}\).

Using the Pythagorean triple 5,12,13, it is easy to find \(\displaystyle \sin y = \frac {12}{13}\).

So substituting all four values into the top equation, we get

\(\displaystyle \csc (x+y) = \frac {1}{\frac {3}{5} \cdot \frac {5}{13} + \frac {4}{5} \cdot \frac {12}{13}} = \frac {65}{63}\)

Example Question #1 : Sec, Csc, Ctan

Find the value of the trigonometric function in fraction form for triangle \(\displaystyle ABC\).

Triangle

What is the secant of \(\displaystyle \angle A\)?

Possible Answers:

\(\displaystyle 24/7\)

\(\displaystyle 7/25\)

\(\displaystyle 25/7\)

\(\displaystyle 24/25\)

\(\displaystyle \frac{25}{24}\)

Correct answer:

\(\displaystyle \frac{25}{24}\)

Explanation:

The value of the secant of an angle is the value of the hypotenuse over the adjacent.

Therefore:

\(\displaystyle sec \angle A = \frac{hypotenuse}{adjacent} = \frac{25}{24}\)

Example Question #1 : Secant, Cosecant, Cotangent

Which of the following is the equivalent to \(\displaystyle \frac{1}{\csc\theta}\)?

Possible Answers:

\(\displaystyle \sec\theta\)

\(\displaystyle \cot\theta\)

\(\displaystyle \sin\theta\)

\(\displaystyle \tan\theta\sin\theta\)

\(\displaystyle \cos\theta\)

Correct answer:

\(\displaystyle \sin\theta\)

Explanation:

Since \(\displaystyle \csc\theta=\frac{1}{\sin\theta}\):

 \(\displaystyle \frac{1}{\csc\theta}=\frac{1}{\frac{1}{\sin\theta}}=1*\frac{\sin\theta}{1}=\sin\theta\)

Example Question #21 : Trigonometry

Soh_cah_toa

For the above triangle, what is \(\displaystyle \sec (\theta)\) if \(\displaystyle o = 8\)\(\displaystyle a = 15\) and \(\displaystyle h = 17\)?

Possible Answers:

\(\displaystyle 0.47\)

\(\displaystyle 2.13\)

\(\displaystyle {}1.13\)

\(\displaystyle 0.53\)

\(\displaystyle 0.88\)

Correct answer:

\(\displaystyle {}1.13\)

Explanation:

Secant is the reciprocal of cosine.

\(\displaystyle \sec \left ( \theta\right ) = \frac{1}{\cos \left ( \theta\right )}\)

It's formula is:

\(\displaystyle \sec(\theta) = \frac{\textup{hypotenuse}}{\textup{adjacent}}\)

Substituting the values from the problem we get,

\(\displaystyle \sec(\theta) = \frac{17}{15} = 1.13\)

 

 

Example Question #22 : Trigonometry

Soh_cah_toa

For the above triangle, what is \(\displaystyle \cot (\theta)\) if \(\displaystyle o = 18\)\(\displaystyle a = 24\) and \(\displaystyle h = 30\)?

Possible Answers:

\(\displaystyle 0.75\)

\(\displaystyle 1.33\)

\(\displaystyle 1.25\)

\(\displaystyle 1.67\)

\(\displaystyle 0.60\)

Correct answer:

\(\displaystyle 1.33\)

Explanation:

Cotangent is the reciprocal of tangent.

\(\displaystyle \cot \left ( \theta\right ) = \frac{1}{\tan \left ( \theta\right )}\)

It's formula is:

\(\displaystyle \cot(\theta) = \frac{\textup{adjacent}}{\textup{opposite}}\)

Substituting the values from the problem we get,

\(\displaystyle \cot(\theta) = \frac{24}{18} = 1.33\)

 

Example Question #1 : Secant, Cosecant, Cotangent

Determine the value of \(\displaystyle cot(\frac{\pi}{4})\).

Possible Answers:

\(\displaystyle \frac{1}{2}\)

\(\displaystyle \infty\)

\(\displaystyle 0\)

\(\displaystyle \frac{\sqrt2}{2}\)

\(\displaystyle 1\)

Correct answer:

\(\displaystyle 1\)

Explanation:

Rewrite \(\displaystyle cot(\frac{\pi}{4})\) in terms of sine and cosine.

\(\displaystyle cot(\frac{\pi}{4})= \frac{cos(\frac{\pi}{4})}{sin(\frac{\pi}{4})}=\frac{\frac{\sqrt2}{2}}{\frac{\sqrt2}{2}}=1\)

Example Question #8 : Secant, Cosecant, Cotangent

Evaluate:  \(\displaystyle sec(60)-csc(45)\)

Possible Answers:

\(\displaystyle 2\sqrt2+2\)

\(\displaystyle 2+\sqrt2\)

\(\displaystyle 2-\sqrt2\)

\(\displaystyle 2-\frac{\sqrt2}{2}\)

\(\displaystyle 2+\frac{\sqrt2}{2}\)

Correct answer:

\(\displaystyle 2-\sqrt2\)

Explanation:

Evaluate each term separately.

\(\displaystyle sec(60)= \frac{1}{cos(60)}=\frac{1}{0.5}= 2\)

\(\displaystyle csc(45)= \frac{1}{sin(45)}= \frac{1}{\frac{\sqrt2}{2}}= \frac{2}{\sqrt2}\times\frac{\sqrt2}{\sqrt2}= \frac{2\sqrt2}{2}=\sqrt2\)

\(\displaystyle sec(60)-csc(45)=2-\frac{2\sqrt2}{2}=2-\sqrt2\)

Learning Tools by Varsity Tutors