Question

Выразить tg(фи) через sin2(фи),cos2(фи)

Answer 1

$tgphi = dfrac{sinphi}{cosphi} =dfrac{2sinphi cosphi}{2cos^2phi} =\\=dfrac{sin2phi}{cos^2phi+1-sin^2phi} =dfrac{sin2phi}{cos2phi+1}$