Question

by using the substitution t=tan x/2, show that cos x + cot x=0 can be written in the form (t-1)(t+1)^3=0.

Answer 1

in the step 4, how did u get( 1-c0s x)/2??

Answer 2

it is formula, normally cos2x=1-2sin^2x from here[ cos(A+B)=cosAcosB-sinAsinB) A=x B=x cox2x=cos^2x-sin^2x and cos^2x+sin^2x=1]
hence, cosx=1-2sin^2(x/2