Question

已知sinα+sin²α=1,求3cos²α+cos的4次方α-2sinα+1

Answer 1

sinα+(sinα)^2=1=(sinα)^2+(cosα)^2

sinα=(cosα)^2

3(cosα)^2+(cosα)^4-2sinα+1

=3(cosα)^2+(sinα)^2-2(cosα)^2+1

=(sinα)^2+(cosα)^2+1

=2