cv02-roge矩阵，旋转向量 ，角度

​​ https://www.zhihu.com/question/340068905/answer/784922951​​

thetta=atan(r21,r11)=atan(-0.7,0.7)=atan(1)=-45度。得到验证

theta=atan(-0.95,0.15)=-81度=负81度。