如何让一个点绕中心旋转

//实现原理根据改变 三角形的正弦定理 余弦定理

- (void)starAnimash:(UIImageView *)imgView

{

    _imgView = imgView;

    

    self.center = CGPointMake(_radius * cosf(_angle) + imgView.center.x, _radius * sinf(_angle) + imgView.center.y);

    

    _timer = [NSTimer scheduledTimerWithTimeInterval:_time target:self selector:@selector(moveView) userInfo:nil repeats:YES];

}

- (void)moveView

{

    self.angle += M_PI_2/30;

    self.center = CGPointMake(self.radius * cosf(self.angle) + _imgView.center.x, self.radius * sinf(self.angle) + _imgView.center.y);

}