Question

sin7度+cos15度sin8度除以cos7度-sin15度sin8度等于多少

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Answer 1

(sin7°+cos15°sin8°)/(cos7°-sin15°sin8°)这里把7°=15°-8°表示.sin7°=sin(15°-8°)=sin15°cos8°-cos15°sin8°cos7°=cos(15°-8°)=cos15°cos8°+sin15°sin8°则上式=sin15°cos8°÷(cos15°cos8°) =sin15°/cos15°=2sin15°cos15°/(2cos15°×cos15°)=sin30°/(cos30°+1)=2-根3