cos^2(70)+cos^2(40)+cos^2(50)
求和:cos(0)+cos(α)+cos(2α)+cos(3α)+……cos(nα)
2sin@+cos@等于?
cos(x^2)dx
cos x>-1/2
化简:2cos
cos
cos(pai/15)×cos(2pai/15)×cos(3pai/15)×cos(4pai/15)×cos(5pai/
(cos 10)^2+(cos 50)^2-sin 40 * sin 80 怎么算
求证:a^2(cos^2b-cos^2c)+b^2(cos^c-cos^2a)+c^2(cos^2a-cos^2b)=0
2(cos x)^2=1+cos 2x,
cos 2x /sin^2 x*cos^2 x不定积分
∫ (1+cos^2 x)/cos^2 x dx =