degree and radian, and the x,y

• $radian=degree \times \frac{\pi}{180}$
• $degree= radian \times \frac{180}{\pi}$

if we have want a angle of 45 degree, then we can calculate

radian = 45 * Math.PI/180

radian = 0.7853981633974483

for the vector of 45 degree, we can get the x and y with sin(θ) and cos(θ)

x = Math.cos(radian)

y = Math.sin(radian)