Basic Trigonometric Identities
Sol A , so since if is in Quadrant IV.
Sol B , so since if is in Quadrant III.
Sol C , so since if is in Quadrant IV. Therefore .
Sol 1 , so since for . Therefore .
Sol 2 , so since if . Then , so .
Sol 3 Since , and so . Therefore since for .
Sol 4 , which can also be written as .
Sol 5 .
Sol 6 .
Sol 7 since for .
Sol 8 since for .
Sol 9 .
Sol 10 .
Sol 12 .
Sol 13 .