SAT II Math I : SAT Subject Test in Math I

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

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Example Questions

Example Question #1 : Sec, Csc, Ctan

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

Possible Answers:

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

\(\displaystyle \sin\theta\)

\(\displaystyle \sec\theta\)

\(\displaystyle \cot\theta\)

\(\displaystyle \cos\theta\)

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 #1 : Secant, Cosecant, Cotangent

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:

\(\displaystyle 0.53\)

\(\displaystyle 0.88\)

\(\displaystyle 0.47\)

\(\displaystyle 2.13\)

\(\displaystyle {}1.13\)

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 #2 : Sec, Csc, Ctan

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:

\(\displaystyle 1.25\)

\(\displaystyle 1.67\)

\(\displaystyle 0.60\)

\(\displaystyle 1.33\)

\(\displaystyle 0.75\)

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 #2 : Sec, Csc, Ctan

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

Possible Answers:

\(\displaystyle 1\)

\(\displaystyle \infty\)

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

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

\(\displaystyle 0\)

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 #554 : Trigonometry

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

Possible Answers:

\(\displaystyle 2-\sqrt2\)

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

\(\displaystyle 2\sqrt2+2\)

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

\(\displaystyle 2+\sqrt2\)

Correct answer:

\(\displaystyle 2-\sqrt2\)

Explanation:

Evaluate each term separately.

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

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

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

Example Question #3 : Sec, Csc, Ctan

Pick the ratio of side lengths that would give sec C.

 10

Possible Answers:

\(\displaystyle \sec C=\frac{AB}{AC}\)

\(\displaystyle \sec C=\frac{AC}{CB}\)

None of the other answers.

\(\displaystyle \sec C=\frac{CB}{AC}\)

\(\displaystyle \sec C=\frac{AC}{AB}\)

Correct answer:

\(\displaystyle \sec C=\frac{CB}{AC}\)

Explanation:

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

Find the ratio of Cosine and take the reciprocal.

\(\displaystyle \cos\theta=\frac{AC}{CB}\rightarrow \sec\theta=\frac{1}{\frac{AC}{CB}}=\mathbf{\frac{CB}{AC}}\) 

 

Example Question #11 : Secant, Cosecant, Cotangent

Evaluate:  \(\displaystyle sec(30)-csc(60)\)

Possible Answers:

\(\displaystyle \frac{\sqrt3-1}{2}\)

\(\displaystyle \frac{1-\sqrt3}{2}\)

\(\displaystyle \sqrt3-1\)

\(\displaystyle \sqrt{3}\)

\(\displaystyle 0\)

Correct answer:

\(\displaystyle 0\)

Explanation:

Recall that \(\displaystyle sec(x) = \frac{1}{cos(x)}\) and \(\displaystyle csc(x) = \frac{1}{sin(x)}\).

Rewrite the expression.

\(\displaystyle sec(30)-csc(60) = \frac{1}{cos(30)}-\frac{1}{sin(60)}\)

The value of \(\displaystyle cos(30) = \frac{\sqrt3}{2}\) and \(\displaystyle sin(60) =\frac{ \sqrt{3}}{2}\).

Since these values are similar, our resulting answer is zero upon substitution.

\(\displaystyle \frac{1}{\frac{\sqrt3}{2}}-\frac{1}{\frac{\sqrt3}{2}} = 0\)

The answer is:  \(\displaystyle 0\)

Example Question #1 : Right Triangles And Similar Triangles

Aas

Find the area of the triangle.

Possible Answers:

\(\displaystyle 12\sqrt{3}\)

\(\displaystyle 6\sqrt{3} + 6\)

\(\displaystyle 6\sqrt{3} + 12\)

\(\displaystyle 12\sqrt{3} + 12\)

\(\displaystyle 18\sqrt{3} + 18\)

Correct answer:

\(\displaystyle 18\sqrt{3} + 18\)

Explanation:

Aas_key

Dropping the altitude creates two special right triangles as shown in the diagram.  Use the area formula of a triangle to get

\(\displaystyle A = \frac {1}{2}bh = \frac {1}{2} \cdot (6 \sqrt{3} + 6) \cdot 6 = 18\sqrt{3} + 18\)

Example Question #1 : Right Triangles And Similar Triangles

Fire tower A is \(\displaystyle 2\) miles due west of fire tower B.  Fire tower A sees a fire in the direction \(\displaystyle 40\) degrees west of north.  Fire tower B sees the same fire in the direction \(\displaystyle 50\) degrees east of north.  Which tower is closer to the fire and by how much?

Possible Answers:

Fire tower B; 0.24 miles

Fire tower A; 1.53 miles

Fire tower A; 0.24 miles

Fire tower B; 1.29 miles

The two fire towers are equidistant to the fire.

Correct answer:

Fire tower B; 0.24 miles

Explanation:

Fire

First, realize that the angles given are from due north, which means you need to find the complements to find the interior angles of the triangle.  This triangle happens to be a right triangle, so the fast way to compute the distances is using trigonometry.

\(\displaystyle \sin 50^\circ = \frac{AF}{2}\)

\(\displaystyle AF \approx 1.53 miles\)

\(\displaystyle \sin 40^\circ = \frac{BF}{2}\)

\(\displaystyle BF \approx 1.29 miles\)

Fire tower B is \(\displaystyle 1.53 - 1.29 = 0.24\) miles closer to the fire.

Example Question #2 : Right Triangles And Similar Triangles

Los

Find the length of side \(\displaystyle AB\).

Possible Answers:

\(\displaystyle 5.0\)

\(\displaystyle 5.8\)

\(\displaystyle 5.3\)

\(\displaystyle 5.2\)

\(\displaystyle 4.9\)

Correct answer:

\(\displaystyle 5.0\)

Explanation:

In an angle-side-angle problem, Law of Sines will solve the triangle. 

First find angle A:

\(\displaystyle 180-(83+44)=53\)

Then use Law of Sines.

\(\displaystyle \frac {AB}{\sin 83^\circ} = \frac {4}{\sin 53^\circ} \rightarrow AB = \frac {4 \sin 83^\circ}{\sin 53^\circ} \approx 5.0\)

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