Question

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

Answer 1

$tg\phi = \dfrac{sin\phi}{cos\phi} =\dfrac{2sin\phi cos\phi}{2cos^2\phi} =\\\\=\dfrac{sin2\phi}{cos^2\phi+1-sin^2\phi} =\dfrac{sin2\phi}{cos2\phi+1}$