Question

помогите с алгеброй, пожалуйста))

Answer 1

$cfrac{2cos^2 alpha tg alpha }{cos^2 alpha -sin^2 alpha } = cfrac{2sin alpha cos alpha }{cos2 alpha } = cfrac{sin2 alpha}{cos2 alpha } =tg2 alpha$

$cfrac{cos15cos30-sin15sin30}{sin60cos15-cos60sin15} = cfrac{cos(15+30)}{sin(60-15)} = cfrac{cos45}{sin45} = ctg45=1$