If you don't need to be strict, you can use a triangular ruler.

If you want a standard point, you must first draw a circle, and then take the diameter of the circle as the hypotenuse of the triangle, and connect any point on the arc with both ends of the diameter to get a right triangle.

1 Make a right angle, and then make the bisector of this right angle to get a right angle and make a right triangle.

2 Make a circle, then make a diameter, and connect any point on the circumference (except the end point of the diameter) with the end point of the diameter to get a right triangle (because the circumferential angle opposite to the diameter is a right angle).

Using the inverse theorem of Pythagorean theorem, that is, to find Pythagorean number, first draw a line segment =a, and then use a ruler to make a triangle with side lengths of 3a, 4a and 5a, which is a right triangle.