Triangle by moving the triangle, rotating it, or reflecting it as in a mirror, any of which give a congruent triangle, or even by rescaling it to give a similar triangle: A non-planar triangle is a triangle which is not contained in a (flat) plane. Some examples of non-planar triangles in non-Euclidean geometries are spherical triangles in spherical geometry and hyperbolic triangles in hyperbolic geometry. While the measures of the internal angles in planar triangles always sum to 180°, a hyperbolic triangle has measures of angles that sum to less than 180°, and a spherical triangle has measures of angles that
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"