All the trigonometric ratios for angle of measures 0^A^0, 30^A^0, 45^A^0, 60^A^0 and 90^A^0 are provided in the following table:. Trigonometry is a vast subject. It’s an essential part of mathematics. Trigonometry starts by examining the triangles,. particularly. the right-angled triangles. Supplementary composite triangles can be built by joining right-angled triangles together. More complex shapes, such as squares, hexagons, circles and ellipses can be constructed from two or more triangles. Finally, the universe we live in can be mapped through the use of triangles. For instance, the Ancient Greeks were able to use trigonometry to calculate the distance from the Earth to the Moon Later trigonometry was developed to be the branch of mathematics that studies about relationships between angles and sides of right triangles. This branch of mathematics defines six important trigonometric ratios which are as follows sine, cosine, tangent, cosecant, secant, cotangent. These are written in short as sin, cos, tan, cosec, sec and cot. In a right triangle, the side opposite to the right angle is known as the hypotenuse, the side that is perpendicular is termed as adjacent and third side is known as base. Trigonometric ratios. are called therefore because all of these are defined as specified relationships between ratios of sides and angles of the right-angled triangles. The ratios sine, cosine and tangent are main ratios; while cosecant, secant and cotangent are the inverse function of sine, cosine, tangent respectively. Let us go ahead in this page and understand more about trigonometric ratios, their definitions, important formulae and sample problems based on those . .