# trig

posted by
**gin**
.

For each expression in column I, choose the expression from column II to complete an identity:

Column I Column II

1. -tanxcosx A. sin^2x/cos^2x

2. sec^2x-1 B. 1/sec^2x

3. sec x/cscx C. sin(-x)

4. 1+sin^2x D.csc^2x-cot^2x+sin^2x

5. cos^2 x E. tanx

I figured #1 is C, #2 is A, And #4 is D, but I am not sure about the rest. Please give answers and explain. Also, for the following, verify that each trig equation is an identity and explain why. NOTE: I using @ to mean angle.

6. cot^2t-1/1+cot^2t = 1-2sin^2t

7. 1-cos@/1+cos@ = 2csc^2@-2csc@cot@-1