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Choice A is correct. A trigonometric ratio can be found using the unit circle, that is, a circle with radius 1 unit. If a central angle of a unit circle in the xy-plane centered at the origin has its starting side on the positive x-axis and its terminal side intersects the circle at a point ^x,yh, then the value of the tangent of the 38 SAT PRACTICE TEST #5 ANSWER EXPLANATIONS SAT ANSWER EXPLANATIONS n MATH: MODULE 1 central angle is equal to the y-coordinate divided by the x-coordinate. There are r 92r r 92 15+2 2 radians in a circle. Dividing 3 by 2 yields 6, which is equivalent to 3. It 92r follows that on the unit circle centered at the origin in the xy-plane, the angle 3 15 is the result of revolutions from its starting side on the positive x-axis followed 2r 92r 2r by a rotation through 3 radians. Therefore, the angles 3 and 3 are coterminal tan 92r tan 2r 2r r angles and e 3 o is equal to e3o. Since 3 is greater than 2 and less than r , it follows that the terminal side of the angle is in quadrant II and forms an angle r 60° of , or , with the negative x-axis. Therefore, the terminal side of the angle 3 - 1 , 3 tan 2r intersects the unit circle at the point f 2 2 p. It follows that the value of e3o 3 2 - tan 92r - is 1, which is equivalent to 3. Therefore, the value of e 3 o is 3. - 2 1 92r tan 92r Choice B is incorrect. This is the value of tan e 3 o , not e 3 o. Choice C is 1 tan 92r incorrect. This is the value of tan r , not b 3 l. Choice D is incorrect. This is the d3n tan r tan 92r value of a3k, not e 3 o.