double & half angle

8. If x is an acute angle, and cos x - , then cos 2x is equal to 1) 6 25 2) = 3) 25 4) 75 9. If e is an acute angle such that sin 8-, 13, what is the value of sin 2 67 1 ) 13 2) 10 3 ) 60 4) 120 169 169 10. Prove the following is an identity for all values of @ for which the expressions are defined: sin a cot a + s + cos 0- sec e 1 1. For all values of x for which the expressions are defined, prove that the following is an identity: cos x + cotx = COS X 1 + csc x 12. For all values of x for which the expressions are defined, prove that the following is an identity: tan x csc x = cotx 1 + tan x Extra Credit: For all values of @ for which the expressions are defined, prove that the following is an identity: cos &cos @+ 1) + sin? a_ sin 8+ tan @ tan &