11. find the exact value by using a half-angle identity. (1 point) sin 22.5° a) negative one half times the square root of quantity two plus square root of two. b) one half times the square root of quantity two plus square root of two. c) negative one half times the square root of quantity two minus square root of two. d) one half times the square root of quantity two minus square root of two 12. find all solutions to the equation in the interval [0, 2π). (1 point) cos x = sin 2x a) pi divided by two. , three pi divided by two. b)pi divided by six. , pi divided by two. , five pi divided by six. , three pi divided by two. c) 0, π d) 0, pi divided by six. , five pi divided by six. , π 13. rewrite with only sin x and cos x. (1 point) sin 2x - cos x a) 2 sin x cos2x b) sin x c) cos x (2 sin x - 1) d) 2 sin x 14. verify the identity. (1 point) cosine of x divided by quantity one plus sine of x plus quantity one plus sine of x divided by cosine of x equals two times secant of x. 15. verify the identity. (1 point) cot x minus pi divided by two. = -tan x