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(sin7+Cos15*sin8)/(Cos7%sin15*sin8)

(sin7+cos15sin8)/(cos7-sin15sin8) =(sin(15-8)+cos15sin8)/(cos(15-8)-sin15sin8) =(sin15cos8-cos15sin8+cos15sin8)/(cos15cos8+sin15sin8-sin15sin8) =sin15cos8/cos15cos8 =sin15/cos15 =2sin15cos15/2cos²15 =sin30/(1+cos30) =2-√3

(sin7+cos15sin8)/(cos7-sin15sin8) =[sin7+cos(7+8)sin8]/[cos7-sin(7+8)sin8] =[sin7+(cos7cos8-sin7sin8)sin8]/[cos7-(sin7cos8+sin8cos7)sin8] =(sin7+cos7cos8sin8-sin7sin²8)/(cos7-sin7sin8cos8-sin²8cos7) =(sin7-sin7sin&sup...

(sin7+cos15sin8)/(cos7-sin15sin8) =[sin7+cos(7+8)sin8]/[cos7-sin(7+8)sin8] =[sin7+(cos7cos8-sin7sin8)sin8]/[cos7-(sin7cos8+sin8cos7)sin8] =(sin7+cos7cos8sin8-sin7sin8)/(cos7-sin7sin8cos8-sin8cos7) =(sin7-sin7sin8+cos7cos8sin8)/...

(sin7+sin8cos15)/(cos7-sin8sin15) =[sin(15-8)+sin8cos15]/[cos(15-8)-sin8sin15] =[(sin15cos8-cos15sin8)+cos15sin8]/[(cos15cos8+sin15sin8)-sin15sin8] =(sin15cos8/(cos15cos8) =sin15/cos15 =tan15 =tan(60-45) =(tan60-tan45)/(1+tan60...

因为cos15°sin8°=12[sin(8°+15°)+sin(8°-15°)=12(sin23°-sin7°)],sin15°sin8°=12(cos7°-cos23°),所以sin7°+cos15°sin8°cos7°?sin15°sin8°=sin23°+sin7°cos23°+cos7°=2sin15°cos8°2cos15°cos8°=tan15°=tan(45°-30°)=tan45°?tan30°1+t...

(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°/...

(sin7°+cos15°sin8°) / (cos7°- sin15°sin8°) =(sin(15-8)°+cos15°sin8°) / (cos(15-8)°- sin15°sin8°) =sin15°cos8°/cos15°cos8° =tan15°

=(sin(15-8)+cos15sin8)/(cos(15-8)-sin15sin8=(sin15cos8-cos15sin8+cos15sin8)/(cos15sin8+sin15cos8-sin15sin8)=sin15/cos15=tan15=tan(45-30)=2-根3

=(sin(15-8)+cos15sin8)/(cos(15-8)-sin15sin8 =(sin15cos8-cos15sin8+cos15sin8)/(cos15sin8+sin15cos8-sin15sin8)=sin15/cos15 =tan15 =tan(45-30) =2-根3

原式=(sin(15°-8°)+cos15°sin8°)/(cos(15°-8°)-sin15°sin8°)=(sin15°cos8°+cos15°sin8°-cos15°sin8°)/(sin15°sin8°+cos15°cos8°-sin15°sin8°)=sin15°cos8°/cos15°cos8°=tan15°

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