Question

Given the point `P(-12/13, -5/13)`, how do you find `sintheta` and `costheta`?

Answer 1

`sin t = - 5/13`
`cos t = - 12/13`

Explanation:

`tan t = y/x = (- 5/13)/(-12/13) = 5/12`.
P and t are located in Quadrant 3.
`cos^2 t = 1/(1 + tan^2 t) = 1/(1 + 25/144) = 144/169`
`cos t = +- 12/13`
Since t is in Quadrant 3, therefor, cos t is negative
`cos t = - 12/13`.
`sin t = tan t.cos t = (5/12)(- 12/13) = - 5/13`