
1. C
The trick to this question is knowing the identity tan^{2} + 1 = sec^{2}. If you didn’t know it, you could have derived the identity from the base identity sin^{2} + cos^{2} = 1 by dividing through the equation by cos^{2}, giving tan^{2} + 1 = sec^{2}. Subtracting 1 from both sides gives tan^{2} = sec^{2} – 1.
Now, substitute into the equation from the question:
The identity tan = sin /cos allows for further simplification:
The only answer choice for that yields a cosine value of 1 is 0.
2. B
For any x, sin^{–1}(sin(x))
= x. So the fraction reduces to
3. C
The first step is to calculate the length of the segment RT.
To do so, use the definition of the sine function, sin =
Next, calculate the length of segment ST using
the cosine function (cos =
Now, the trick is to see that length segment ST is actually the sum of the radii of the two circles (SU + UT). Moreover, the length of segment RT = UT because they are both radii of the larger circle. Since you know the length of segment RT (and so, segment UT), you can subtract this value from segment ST to get the length of segment SU (which is also the radius of the smaller circle and the answer):
4. C
The figure gives a nonright triangle, so you can’t
use the basic trigonometric functions to find BC.
But you are given the measures of two angles and the side between
them, so you can use the law of sines:
First, find the measure of , using the rule that the sum of
angles in a triangle is 180: B = 180 – 72 – 50
= 58º. Plug the value of into the law of
sines:
5. E
Since you have the measures of two sides and the angle between them, you can start with the law of cosines to find c. Plug the given values into the law of cosines formula: c^{2} = 5^{2} + 7^{2} + 2(5)(7) cos 110º. Working this out, you get c ≈ 7.08. Now that you have the measure of the side opposite , you can use the law of sines to find a. Substitute the values into the formula, and solve the equation:
Taking the arcsine, ≈ 68.3º.
6. D
sin^{–1 }2 is undefined, because
no angle exists whose sine is greater than 1. tan
7. C
There are two easy ways to simplify the given expression. Both involve using identities. The first way is to immediately factor the expression into (1 – cos^{2}x)(1 + tan^{2}x). Then, using the identities 1 – cos^{2}x = sin^{2}x and 1 + tan^{2}x = sec^{2}x, the expression is simplified to sin^{2}(x)sec^{2}(x), which can be furthered simplified:
The other way takes slightly longer but requires the use of fewer identities.
8. A
Without knowing the doubleangle identity for sine,
you could have found the arcsine of
