Trigonometry, The word trigonometry has deen derived from three Greek words TREI means THREE, GONI means ANGLE and METRON means MEASURMENT. So, mainly it can also be described, the measurement of the triangle is called TRIGONOMETRY.

As a triangle has tree sides name as HYPOTINOUS, PERPENDICULAR and BASE. And these three sides make three angles with each another. The sum of all three angles should be 180⁰.

Let A, B and C are the sides of triangle.so,

        

Angle, The maximum angle of a triangle is 180⁰ and minimum angle is 0⁰. It is depend on the rotation of the sides of the triangle. If a side of the triangle is parallel to other then the angle between these sides is 0⁰ and if one side is antiparallel to the other then the angle between these two sides is 180⁰. In the same way if one side is perpendicular to the other side then the angle is 0f 90⁰. It’s also described as if one side makes half (1/2) rotation anti clock wise from the other then it make angle of 180⁰. And if it makes quarter (1/4) rotation then it makes 90⁰ angle.

EXAMPLE:

                   We know that

One rotation= 360⁰

Half rotation=180⁰

Quarter rotation=90⁰

Sum of all three angles most be equal to 180⁰.Let a triangle has tri sides A, B and C makes three angles α, β and γ respectively. So,

                      α + β + γ = 180⁰