cos(X-30°)=4/5 X的范围在30°到90°,求tanx

问题描述:

cos(X-30°)=4/5 X的范围在30°到90°,求tanx

cos(X-30°)=4/5,X的范围在30°到90°
X的范围在30°到90°
sin(x-30°)=3/5
tan(X-30°)=3/4
tanx=[9+4*3^(1/2)]/[12-3^3(1/2)]