cos600 =cos(2*360-120) =cos(-120) =cos120 =-1/2
cos120度应该如何做?是不是180度-60度=120度.cos在第二象限为负数.cos45度=2分之一所以就是负的2
Cos60度=1/2,则cos120=?sin120=?
2(cos x)^2=1+cos 2x,
∫ (1+cos^2 x)/cos^2 x dx =
Cos x=-1/2
cos平方1度+cos平方2度+cos平方3度+.+cos平方89度=?
求值:cos^2 1度+cos^2 2度+…+cos^2 180度=___.
化简(1-sin^6 a-cos^6 a)/(cos^2 a-cos^4 a)==
求证:sin^2/(sin-cos) - (sin+cos)/(tan^2 -1) =sin+cos
Cos(a+b)*cos(a-b)=1/5 求cos ^2-sin^2
已知1+cosα/cosα=-1/2求cosα/sinα-1
sin120°= cos120°=