求值:sin^2α+sin^2β-sin^2α×sin^2β+cos^2α×cos^2β

问题描述:

求值:sin^2α+sin^2β-sin^2α×sin^2β+cos^2α×cos^2β

sin²α+sin²β-sin²α×sin²β+cos²α×cos²β=sin²α-sin²α×sin²β+cos²α×cos²β+sin²β=sin²α×(1-sin²β)+cos²α×cos²...