# CGContextAddArcToPoint Adds an arc of a circle to the current path, using a radius and tangent points. ``` extern void CGContextAddArcToPoint(CGContextRef c, CGFloat x1, CGFloat y1, CGFloat x2, CGFloat y2, CGFloat radius); ``` ## Parameters `c` A graphics context whose current path is not empty. `x1` The x-value, in user space coordinates, for the end point of the first tangent line. The first tangent line is drawn from the current point to (x1,y1). `y1` The y-value, in user space coordinates, for the end point of the first tangent line. The first tangent line is drawn from the current point to (x1,y1). `x2` The x-value, in user space coordinates, for the end point of the second tangent line. The second tangent line is drawn from (x1,y1) to (x2,y2). `y2` The y-value, in user space coordinates, for the end point of the second tangent line. The second tangent line is drawn from (x1,y1) to (x2,y2). `radius` The radius of the arc, in user space coordinates. ## Discussion This method calculates two tangent lines—the first from the current point to the point `(x1, y1)`, and the second from the point `(x1, y1)` to the point `(x2, y2)`—then calculates the start and end points for a circular arc of the specified radius such that the arc is tangent to both lines. Finally, this method approximates that arc with a sequence of cubic Bézier curves and appends those curves to the current path. If the starting point of the arc (that is, the point where a circle of the specified radius must meet the first tangent line in order to also be tangent to the second line) is not the current point, this method appends a straight line segment from the current point to the starting point of the arc. The ending point of the arc (that is, the point where a circle of the specified radius must meet the second tangent line in order to also be tangent to the first line) becomes the new current point of the path. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)