1cos 2x = 1 - 2sin^2 x
1-2sin^2 x-sinx=0
1-sinx - 2sin^2 x=0
(1-2sinx)(1+sinx)=0
Equals zero if sinx =1/2 or sinx = -1
3 Answers
1Express cos 2x in terms of sin x. You will then have a quadratic, which is easily dealt with, as sin x can only range from -1 to +1.
1
1Arshad....i think he is asking for general rather than principal values.....:-)