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

(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) =(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

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°=sin7°+cos(7°+8°)sin8°cos7°?sin(7°+8°)sin8°=sin7°+(cos7°cos8°?sin7°sin8°)sin8°cos7°?(sin7°cos8°+sin8°cos7°)sin8°=sin7°+cos7°cos8°sin8°?sin7°sin28°cos7°?sin7°sin8°cos8°?sin28°cos7°=sin7°?sin7°s...

为了表示方便我就不写°了直接用数字表示度数,虽然这样不规范. (sin7+cos15sin8)/(cos7-sin15sin8) ====积化和差 =[sin7+(sin23-sin7)*0.5]/[cos7+(cos23-cos7)*0.5] =(0.5sin7+0.5cos23)/(0.5cos7+0.5cos23) ====约分,和差化积 =(sin15*sin8)/(c...

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(sin6+cos15*sin9)/(cos6-sin15*sin9) =[sin(15-9)+cos15*sin9]/[cos(15-9)-sin15sin9] =(sin15cos9-cos15sin9+cos15sin9)/(cos15cos9+sin15sin9-sin15sin9) =(sin15cos9)/(cos15cos9) =sin15/cos15 =tan15 =(1-cos30)/sin30 =2-√3

cos7=cos(15-8)=cos15cos8+sin15sin8 到这里就知道你又打少括号,在害人了 (cos7°-sin15°sin8°)/cos8°=cos15cos8/cos8=cos15 虽然求到这里,还是觉得,还是只是化简题而以,一定要求值,会出来连环根号 cos15=根号[(2cos15^2-1+1)/2]=根号[(co...

sin15º=(√6-√2)/4≈0.6503 cos15°=(√2/4)(√3-1)≈0.9659 详解: sin15º=sin(45º-30º)=sin45ºcos30º-cos45ºsin30º=√2/2*√3/2-√2/2*1/2=(√6-√2)/4≈0.6503 cos15°=cos(45°-30°)=cos45°cos30°+sin45°sin30°.=...

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