为什么phase shift为90度

为什么phase shift为90度

find each value by referring to the graphs of the trigonometric function.
根据(三角)函数图像，找到下列三角函数的值
1、sin(720°) = sin(0°+2*360°)= sin 0 °=0
2、cos(540°) = cos(180°+360°) = cos 180°= -1
3、csc(720°) = 1/sin(720°) = 1/sin 0 ° = ∞ No significance


find the values of  for which each equation is true.
1、sin  = -1 ，period T=360°，so  = -90°+ n*360°, n is a integer
2、tan  =0， period T=180°，so  = n*180°,n is a integer


state the amplitude(振幅), period(周期), and phase shift(相移,ω+∮,=0的值 ) for each function.
1、Y=-2sin ，amplitude A= -2， period T= 360°， phase shift 为 0°
2、Y=-3sin 4 ，amplitude A= -3， period T= 90°， phase shift 为 0°
3、Y=2.5cos(+180度)，mplitude A= 2.5， period T= 360°， phase shift 为 180°


write an equation of the sine function with each amplitude, period, and phase shit.

amplitude=0.75, period = 360度, phase shift=30度
0.75sin(x+30°)

write an equation of the cosine function with each amplitude, period,and phase shift.

amplitude=3.75,period =90度, phase shift = 4度.
3.75cos(4x+4°)