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°