Tangent segments to a circle from a point outside the circle are congruent. The measure of an inscribed angle equals half the measure of the intercepted arc. Angles inscribed in the same arc are congruent. Every angle inscribed in a semicircle is a right angle. The opposite angles of a quadrilateral inscribed in a circle are supplementary.
Parallel lines intercept congruent arcs on a circle.
The arc length equals the degree measure of the arc divided by 360, times the circumference. The hypotenuse is the side opposite the right angle is a right triangle. Andy three positive integers that work in the Pythagorean formula are called triplets. If the lengths of three sides of a triangle work in the pythagorean formula, then the triangle is a right triangle. If you multiply the lengths of all three sides of any right triangle by the same number, the resulting triangle will be a right triangle.