#import <math.h>
#import <UIKit/UIKit.h>
#import <CoreGraphics/CoreGraphics.h>
float phi = atan2(y2 - y1, x2 - x1); // substitute x1, x2, y1, y2 as needed
float tip1angle = phi - M_PI / 4; // -45°
float tip2angle = phi + M_PI / 4; // +45°
float x3 = x2 - h * cos(tip1angle); // substitute h here and for the following 3 places
float x4 = x2 - h * cos(tip2angle);
float y3 = y2 - h * sin(tip1angle);
float y4 = y2 - h * sin(tip2angle);
CGPoint arrowStartPoint = CGPointMake(x1, y1);
CGPoint arrowEndPoint = CGPointMake(x2, y2);
CGPoint arrowTip1EndPoint = CGPointMake(x3, y3);
CGPoint arrowTip2EndPoint = CGPointMake(x4, y4);
CGContextRef ctx = UIGraphicsGetCurrentContext(); // assuming an UIView subclass
[[UIColor redColor] set];
CGContextMoveToPoint(ctx, arrowStartPoint.x, arrowStartPoint.y);
CGContextAddLineToPoint(ctx, arrowEndPoint.x, arrowEndPoint.y);
CGContextAddLineToPoint(ctx, arrowTip1EndPoint.x, arrowTip1EndPoint.y);
CGContextMoveToPoint(ctx, arrowEndPoint.x, arrowEndPoint.y);
CGContextAddLineToPoint(ctx, arrowTip2EndPoint.x, arrowTip2EndPoint.y);
これが役立つことを願っています:)