Draw shapes with the Triangle tool

Choose the Shape tool    (U) and select the Triangle tool  () from the available options.

In the shape tool options bar,  set Mode, Fill, Stroke, W, H, Path operation, Path alignment, Path arrangement, and Additional shape and path options

Position the pointer on the canvas and click and drag to draw a triangle shape on a new shape layer. 

Hold the Shift key while dragging to create an equilateral triangle. As an alternative, you can click on the canvas and specify Width, Height, and Corner Radius, and have the option to check Equilateral and From Center, if desired.

To change the radius of the corners, click on the circle inside the shape, and drag it inward. To rotate the triangle, click on the rotate handle that appears as you hover over your shape on the canvas. To resize the triangle, click and drag any of the transform squares. To move the triangle, use the move tool ().