Can someone please prove this equation is an identity. Cos^2 X - sin^2 X = 2cos^2 x - 1 Can someone give me some tips for proving indentity, aside knowing the basic identities,pytho indetites For example when to factor, . And when to multitiply an identity 1-cost/1-cost to prove an identity. And also when will I know if I have to simplify the other side to prove an identity Thank you Can someone please prove this equation is an identity. Cos^2 X - sin^2 X = 2cos^2 x - 1 Can someone give me some tips for proving indentity, aside knowing the basic identities,pytho indetites For example when to factor, . And when to multitiply an identity 1-cost/1-cost to prove an identity. And also when will I know if I have to simplify the other side to prove an identity Thank you Cos^2 X - sin^2 X = 2cos^2 x - 1 Can someone give me some tips for proving indentity, aside knowing the basic identities,pytho indetites For example when to factor, . And when to multitiply an identity 1-cost/1-cost to prove an identity. And also when will I know if I have to simplify the other side to prove an identity Thank you Solution cos2x - sin2x= 2 cos2x-1 RHS: 2 cos2x-1 [ from sin2x + cos2x=1] =2 cos2x- ( sin2x + cos2x) = 2 cos2x- sin2x - cos2x = cos2x - sin2x = LHS hence proved.