Question

Why trigonometry using only right triangle?

Answer 1

Hi as you said the 6 trigonometric ratios are defined based on a right triangle.
But it is not restricted to right triangles.
There something called trigonometric laws of triangles which can be applied to any type of triangles. Consider the figure drawn.
A triangle with angles A,B and C with opposite edges a,b and c respectively.
The sine law states that
a/sin A = b/ sin B =c/sin C
Hope this helps.

Answer 2

Answer:

Step-by-step explanation:

We use Right triangles because "sin" which was introduced by ramanujan described it as half chord. Since line drawn from chord to center is 90 degree therefore we stik to right triangle.