Question

(1+ctg^2a)(1-sin^2a) упростить

Answer 1

$(1+ctg^2a)(1-sin^2a)=1*1-1*sin^2a+ctg^2a-ctg^2a*sin^2a=\ =1-sin^2a+ctg^2a- frac{cos^2a*sin^2a}{sin^2a} =cos^2a+ctg^2a-cos^2a=ctg^2a$