TanA=-2

问题描述:

TanA=-2
0.5(SinA)^2+0.4(CosA)^2
求最后的值是多少?

0.5(SinA)^2+0.4(CosA)^2 =0.4(sin^2a+cos^2a)+0.1sin^2a因为sin^2a+cos^2a=1,所以有(1的妙用):=0.4+0.1*sin^2a/(sin^2a+cos^2a)上下同除以sin^2a=0.4+0.1*1/(1+tan^2a)=0.4+0.1*1/(1+4)=0.4+0.02=0.42注:sin^2a...