求下列各式的值sin15cos15;cos²π/8-sin²π/8tan22.5/1-tan²22.5;2cos²22.5-1
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![求下列各式的值sin15cos15;cos²π/8-sin²π/8tan22.5/1-tan²22.5;2cos²22.5-1](/uploads/image/z/761134-22-4.jpg?t=%E6%B1%82%E4%B8%8B%E5%88%97%E5%90%84%E5%BC%8F%E7%9A%84%E5%80%BCsin15cos15%3Bcos%26sup2%3B%CF%80%2F8-sin%26sup2%3B%CF%80%2F8tan22.5%2F1-tan%26sup2%3B22.5%EF%BC%9B2cos%26sup2%3B22.5-1)
求下列各式的值sin15cos15;cos²π/8-sin²π/8tan22.5/1-tan²22.5;2cos²22.5-1
求下列各式的值
sin15cos15;
cos²π/8-sin²π/8
tan22.5/1-tan²22.5;
2cos²22.5-1
求下列各式的值sin15cos15;cos²π/8-sin²π/8tan22.5/1-tan²22.5;2cos²22.5-1
1,sin60=sin(45+15)=sin45cos15+sin15cos45
sin30=sin(45-15)=sin45cos15-sin15cos45 相加 sin45cos15=(√3+1)/4
2,cos2a=cos²a-sin²a cos²π/8-sin²π/8=cosπ/4=√2/2
3,tan45=tan2×22.5 =2tan22.5/1-tan²22.5 tan22.5/1-tan²22.5=(tan45)/2=1/2
4,2cos²22.5-1=cos2×22.5=cos45=√2/2
1,sin60=sin(45+15)=sin45cos15+sin15cos45
sin30=sin(45-15)=sin45cos15-sin15cos45 相加 sin45cos15=(√3+1)/4
2,cos2a=cos²a-sin²a cos²π/8-sin²π/8=cosπ/4=√2/2
3,tan45=tan2×22.5 =2tan22.5/1-tan²22.5 tan22.5/1-tan²22.5=(tan45)/2=1/2
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