Right triangle right triangle, see the hyperbolic triangle of a hyperbolic sector. 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. 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"
Sum of angles of a triangle sum of all three exterior angles, that equals to 360° in the Euclidean case (as for any convex polygon), is less than 360° in the spherical case, and is greater than 360° in the hyperbolic case. In the differential geometry of surfaces, the question of a triangle's angular defect is understood as a special case of the Gauss-Bonnet theorem where the curvature of a closed curve is not a function, but a measure with the support in exactly three points – vertices of a triangle. Sum of angles of a triangle In several geometries, a triangle has three "vertices" and