证明:sin^2a+sin^2β-sin^2a*sin^2β+cos^2a*cos^2β
=sin^2a+sin^2β-sin^2a*sin^2β+(1-sin^2a)(1-sin^2β)
=sin^2a+sin^2β-sin^2a*sin^2β+1-sin^2a-sin^2β+sin^2a*sin^2β
=1
证明:sin^2a+sin^2β-sin^2a*sin^2β+cos^2a*cos^2β
=sin^2a+sin^2β-sin^2a*sin^2β+(1-sin^2a)(1-sin^2β)
=sin^2a+sin^2β-sin^2a*sin^2β+1-sin^2a-sin^2β+sin^2a*sin^2β
=1