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sin255度等于多少啊

sin255°=sin(180°+75°)= -sin75°= -sin(30°+45°)= -sin30°cos45°-cos30°cos45°= -(1/2)*(√2/2)-(√3/2)*(√2/2)= -(√6+√2)/4 .

sin(255) = sin(180+75) = -sin(75)sin(75) = sin(30+45) = sin30cos45 + cos30*sin45 = 1/2 * 根2/2 + 根3/2 * 根2/2 = (根2+根6)/4所以sin(255) = -(根2+根6)/4

sin255° =sin(180°+75°) = -sin75° = -sin(30°+45°) = -sin30°cos45°-cos30°cos45° = -(1/2)*(√2/2)-(√3/2)*(√2/2) = -(√6+√2)/4 .

sin(255)=sin(180+75)=-sin75=-sin(30+45)=-(sin30cos45+cos30sin45)=-(√2/4+√6/4)=-√2(1+√3)/4

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#include <stdio.h>#include <conio.h>#include <math.h>#define P 3.1415926/180int main(){ /*Sin15度乘以COS75度+COS15度乘以Sin255度*/ printf("%f",sin(15*P)*cos(75*P) + cos(15*P)*sin(255*P)); getch(); }/*运行结果: -0.866025*/

cos255度= cos(-255度)= cos(-255度+360度) = cos(105度) = cos(90度+15度) = - sin15度

sin255°=-sin75°=-cos15°=-√(cos30°+1)/2=-(√6+√2)/4

255=180+75 所以 sin(255度)=-sin(75度) 所以 cos(75度)cos(15度)-sin(255度)sin(15度)=cos(75度)cos(15度)+sin(75度)sin(15度)=cos((75-15)度)=cos(60度)=1/2

sin(180+15)-sin(270-15)=0*sin15+cos180*sin15-(-1*cos15-0*sin15)=-sin15+cos15=(√ ̄2)/2

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