Question

if sinA-cosA=0, sin^4+cos^4=?

Answer 1

[tex]sin^4+cos^4 = sin^4+cos^4 - 2sin^2cos^2 + 2sin^2cos^2 = (sin^2 - cos^2)^2 + 2sin^2cos^2 = [tex]sinA = cosA =)Tan a = 1 =) a = 45  2sin^2acos^2a = 2sin^245cos^245                           = 2 *1/2*1/2 = 1/2  [/tex][/tex]
∴$sin^4+cos^4 = 1/2$