cos75°-cos15°=请详细解答

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cos75°-cos15°=请详细解答cos75°-cos15°=请详细解答cos75°-cos15°=请详细解答原式=cos(60+15)-cos15=cos60cos15-sin60sin15-c

cos75°-cos15°=请详细解答
cos75°-cos15°=
请详细解答

cos75°-cos15°=请详细解答
原式=cos(60+15)-cos15
=cos60cos15-sin60sin15-cos15
=1/2cos15-√3/2sin15-cos15
=-1/2cos15-√3/2sin15
=-(sin30cos15+cos30sin15)
=-sin45
=-√2/2