Question

人教必修4数学求证：1.tan2(平方)x-sin2x=tan2x*sin2x 2.(cosx-1)2(平方)+sin2

Answer 1

1.tan^2x-sin^2x=sin^2x/cos^2-sin^2x=sin^2x(1/cos^2-1)=sin^2x[(1-cos^2)/cos^2]=sin^2x(sin^2x/cos^2x)=tan^2x*sin^2x

2.(cosx-1)^2+sin^2x=(cos^2x-2cosx+1)+sin^2x=1+1-2cosx