<P> For the expression of hyperbolic functions as ratio of the sides of a right triangle, see the hyperbolic triangle of a hyperbolic sector . </P> <P> The values of the trigonometric functions can be evaluated exactly for certain angles using right triangles with special angles . These include the 30 - 60 - 90 triangle which can be used to evaluate the trigonometric functions for any multiple of π / 6, and the 45 - 45 - 90 triangle which can be used to evaluate the trigonometric functions for any multiple of π / 4 . </P> <P> Let H, G, and A be the harmonic mean, the geometric mean, and the arithmetic mean of two positive numbers a and b with a> b . If a right triangle has legs H and G and hypotenuse A, then </P> <Dl> <Dd> A H = A 2 G 2 = G 2 H 2 = φ (\ displaystyle (\ frac (A) (H)) = (\ frac (A ^ (2)) (G ^ (2))) = (\ frac (G ^ (2)) (H ^ (2))) = \ phi \,) </Dd> </Dl>

Are all sides of a right triangle equal