Question

cos⁴a-sin⁴a-cos2a
РАЗЛОЖИТЕ НА множители

Answer 1

cos^4a - sin^4a = (cos^2a + sin^2a)(cos^2a - sin^2a) = 
= cos^2a - sin^2a 

cos^2a - sin^2a - (cos^2a - sin^2a) = (cos^2a - sin^2a)*(1 - 1) = 0