1+ctg^4a=? решите по

Question

1+ctg^4a=? решите по

Answer 1

1+(1+сos2a)²/(1-cos2a)²=(1-2cos2a+cos²2a+1+2cos2a+cos²2a)/(1-cos²2a)=
=2(1+cos²2a)/(1-cos2a)²