已知0已知0已知0tana/2=1/2sina=2tana/(1+tan^2a)=4/5cosa=3/5cos(β-a)=√2/10 sin(β-a)=4√6/10sinβ=sin(β-a+a)=sin(β-a)cosa+cos(β-a)sina=4√6/10*3/5+√2/10 *4/5=2(√6+√2)/25
已知0tana/2=1/2sina=2tana/(1+tan^2a)=4/5cosa=3/5cos(β-a)=√2/10 sin(β-a)=4√6/10sinβ=sin(β-a+a)=sin(β-a)cosa+cos(β-a)sina=4√6/10*3/5+√2/10 *4/5=2(√6+√2)/25