Question

упростите 2sin^2a-1/1-2cos^2a

Answer 1

$cos2alpha=2cos^2alpha-1=1-2sin^2alpha$ - косинус двойного угла

$displaystyle dfrac{2sin^2alpha-1}{1-2cos^2alpha}=dfrac{-(1-2sin^2alpha)}{-(2cos^2alpha-1)}=dfrac{cos2alpha}{cos2alpha}=1$