10. Rewrite with only sin x and cos x. (1 point)sin 2x - cos 2x a) 2 sinx cosx - 1 + 2 sin2x b) 2 sin x cos2x - 1 + 2 sin2x c) 2 sin x cos2x - sin x + 1 - 2 sin2x d) 2 sin x cos2x - 1 - 2 sin2x11. 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 two15. Verify the identity. (1 point)cot x minus pi divided by two. = -tan xNEED HELP ASAP PLEASEEEE!!!

10. Rewrite with only sin x and cos x.
sin 2x - cos 2x
sin2x = 2sinxcosx
cos2x = (cosx)^2 - (sinx)^2 = 2(cosx)^2 -1 = 1- 2(sinx)^2 sin2x- cos2x=2sinxcosx-(1- 2(sinx)^2=2sinxcosx-1+2(sinx)^2 sin2x- cos2x=2sinxcosx-1+2(sinx)^2 the answer is the letter b) 2 sin x cos2x - 1 + 2 sin2x

11. Find the exact value by using a half-angle identity. sin 22.5°Using the half angle formula you get:sin2(θ)=12[1−cos(2θ)]if θ=22.5° then 2θ=45°so you get:sin2(22.5°)=12[1−cos(45°)]sin2(22.5°)=12[1−√2/2]=2−√24and square root both sides:sin(22.5°)=±√2−√24=±0.382so 
sin(22.5°)=0.382the answer is the letter D) one half times the square root of quantity two minus square root of two
15. Verify the identity. 
cot x minus pi divided by two. = -tan x
Cot(x-pi/2)=-tan(x)
 sin(A − B) = sin A cos B − cos A sin B
sin(x – pi/2) = sin x cos (pi/2) − cos x sin (pi/2)=-cosx
 
cos(A − B) = cos A cos B − sin A sin B
cos(x− pi/2) = cos x cos pi/2 − sin x sin pi/2=-sinx
 Cot(x-pi/2)=cos(x-pi/2)/sin(x-pi/2)
= (-sinx)/(-cosx)=-tanx--------------ok