sin15°-根号下3cos15°等于多少?E.sin15°-根号下3cos15°= 2(sin15°cos60°-cos15°sin60°)为什么?

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sin15°-根号下3cos15°等于多少?E.sin15°-根号下3cos15°= 2(sin15°cos60°-cos15°sin60°)为什么?
sin15°-根号下3cos15°等于多少?
E.sin15°-根号下3cos15°
= 2(sin15°cos60°-cos15°sin60°)
为什么?

sin15°-根号下3cos15°等于多少?E.sin15°-根号下3cos15°= 2(sin15°cos60°-cos15°sin60°)为什么?
sin15°-根号下3cos15°
= 2(sin15°cos60°-cos15°sin60°)
= 2sin(15°-60°)
= -2sin45°
= -2*√2/2
= -√2

=2*(sin15*1/2-cos15*√3/2)
=2(sin15cos60-cos15sin60)
=2sin(15-60)
=2sin(-45)
=-2sin45
=-√2

sin15°-根号下3cos15°
=2[(1/2)sin15°-(根号下3/2)cos15°]
=-2[sin60°cos15°-cos60°sin15°]
=-2sin45°
=-根号2