1.已知cosa=3/5 a属于(0,π/2)求sin(a-π/6)的值
问题描述:
1.已知cosa=3/5 a属于(0,π/2)求sin(a-π/6)的值
2.已知tana=-3/4 π
答
1.cosa=3/5,sina=根号下(1-(cosa)^2)=4/5
sin(a-π/6)=sinacosπ/6-cosasinπ/6=
2.sina/cosa=tana=-3/4,(sina)^2+(cosa)^2=1,因为π