画一个三角形

Question

我试图让用户绘制一个三角形。我得到了起点和终点，并使用公式找到等边三角形的第三个点来创建三角形，但它似乎没有任何想法我怎么能做到这一点？也许使用一个圆圈，但我不知道该怎么做。这是我当前的代码。

NSValue *point = [_path objectAtIndex:0];
CGPoint startPoint = point.CGPointValue;

point = [_path lastObject];
CGPoint endPoint = point.CGPointValue;

 CGPoint thirdPoint = CGPointMake(((startPoint.x+endPoint.x)/2), (((startPoint.x-endPoint.x)/2)*(tan(60))+1));
 UIBezierPath *triangle = [UIBezierPath bezierPath];
 [triangle moveToPoint:startPoint];
 [triangle addLineToPoint:endPoint];
 [triangle addLineToPoint:thirdPoint];
 [triangle addLineToPoint:startPoint];
 triangle.lineWidth=size;

Answer 1

这应该可以计算等边三角形的第三个点：

CGPoint startPoint = ..., endPoint = ...;

CGFloat angle = M_PI/3; // 60 degrees in radians
// v1 = vector from startPoint to endPoint:
CGPoint v1 = CGPointMake(endPoint.x - startPoint.x, endPoint.y - startPoint.y);
// v2 = v1 rotated by 60 degrees:
CGPoint v2 = CGPointMake(cosf(angle) * v1.x - sinf(angle) * v1.y,
                         sinf(angle) * v1.x + cosf(angle) * v1.y);
// thirdPoint = startPoint + v2:
CGPoint thirdPoint = CGPointMake(startPoint.x + v2.x, startPoint.y + v2.y);

UIBezierPath *triangle = [UIBezierPath bezierPath];
[triangle moveToPoint:startPoint];
[triangle addLineToPoint:endPoint];
[triangle addLineToPoint:thirdPoint];
[triangle closePath];
// ...