Trigonometric functions describe the relation between the sides and angles of a right triangle. The trigonometric functions include the following 6 functions: sine, cosine, tangent, cotangent, secant, and cosecant. For each of these functions, there is an inverse trigonometric function. They are used for modelling many different natural and mechanical phenomena (populations, waves, engines, acoustics, electronics, UV intensity, growth of plants and animals, etc.). The trigonometric graphs in this chapter are periodic, which means the shape repeats itself exactly after a certain amount of time. In the previous chapters, we have learnt that all trigonometric functions are periodic functions, so here we shall draw their graphs on the intervals of lengths equal to their periods.