Question

Prove That :cot4A = 1-8sin^2 A+8sin^4 A

Answer 1

cos4x as
cos2(2x) =1-2sin2(2x)
             =1-2(2sinx . cosx)2                          { sin2x = 2sinx. cosx}
             =1-2(4sin2x.cos2x)
            =1-8sin2x.cos2x
LHS=RHS

5 years agoshivang belwariar35 Pointscos4x = cos2(2x)
 
2cos^2(2x) - 1
 
2(cos2x)^2 -1
 
2[(2cosx -1 )]^2 -1
 
2[(4cos^2(x)+1-4cox)] -1
 
8cos^2(x) - 8cosx +1u should do somewhat like this