Question

Given the point `P(-3/5, 4/5)`, how do you find `sintheta` and `costheta`?

Answer 1

Please see the explanation.

Explanation:

Given any point A(x, y)

`x = (sqrt(x^2 + y^2)) cos(theta)` and `y = (sqrt(x^2 + y^2))sin(theta)`

In the case of point `P(-3/5, 4/5)`, it is a happy coincidence that

`sqrt((-3/5)^2 + (4/5)^2) = 1`

Therefore:

`-3/5 = cos(theta)` and `4/5 = sin(theta)`