Question

6.14 помогите решить

Answer 1

$\displaystyle \frac{\sin^4a-\sin^2a+\cos^2a}{\cos^3a}=\frac{\sin^2a(\sin^2a-1)+\cos^2a}{\cos^3a}=\\\\=\frac{\sin^2a\cdot(-\cos^2a)+\cos^2a}{\cos^3a}=\frac{\cos^2a(1-\sin^2a)}{\cos^3a}=\frac{\cos a}{\cos a}=\boxed{1}\\\\\\\sin^2a+\cos^2a=1$