cos(J1/4)=根号下[1-sin(J1/4)的平方}
求出 sin(J1/4)={根号下3}/2
cos^2(Л/4)=2sin(J1/4)*cos(J1/4),
就求出来了 开动脑筋作数学题,很有趣的!
COS(13/9)派等于多少?cos(13/9)π=cos(2π-5/9π)=cos5/9π=cos(π/2 π/18)= - sin(π/18)
cos(J1/4)=根号下[1-sin(J1/4)的平方}
求出 sin(J1/4)={根号下3}/2
cos^2(Л/4)=2sin(J1/4)*cos(J1/4),
就求出来了 开动脑筋作数学题,很有趣的!
COS(13/9)派等于多少?cos(13/9)π=cos(2π-5/9π)=cos5/9π=cos(π/2 π/18)= - sin(π/18)