Question

Сократить дробь.
Sinx + sin3x/cos^2x

Answer 1

$\frac{Sinx+Sin3x}{Cos ^{2}x }= \frac{2Sin \frac{x+3x}{2}Cos \frac{x-3x}{2} }{Cos ^{2}x }= \frac{2Sin2xCosx}{Cos ^{2}x }= \frac{4SinxCosx}{Cosx}=4Sinx$