sin15°-根号下3cos15°等于多少?
问题描述:
sin15°-根号下3cos15°等于多少?
E.sin15°-根号下3cos15°
= 2(sin15°cos60°-cos15°sin60°)
为什么?
答
sin15°-根号下3cos15°
= 2(sin15°cos60°-cos15°sin60°)
= 2sin(15°-60°)
= -2sin45°
= -2*√2/2
= -√2sin15°-根号下3cos15°= 2(sin15°cos60°-cos15°sin60°)为什么sin15°-√3 cos15°= 2*(sin15°*1/2-cos15°*√3/2)= 2(sin15°cos60°-cos15°sin60°)2*(sin15°*1/2-cos15°*√3/2)= 2(sin15°cos60°-cos15°sin60°)为什么2*(sin15°*1/2-cos15°*√3/2)= 2(sin15°cos60°-cos15°sin60°)为什么∵1/2 = cos60°,√3/2 = sin60°