sin x = 1/3,360度

sinx是周期函数,周期T=360度,在360度至540度区间的正弦值和0度至180度的值相等,
设y=sin(x/2)+cos(x/2),
两边平方,
y^2=[sin(x/2)]^2+[cos(x/2)]^2+2sin(x/2)cos(x/2)
=1+sinx
=4/3,
0°