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

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Answer 1 · 2016-11-05T17:08:15

Please see the 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 $4/5 = sin(theta)$

Given the point P(-3/5, 4/5)P(-3/5, 4/5), how do you find sinthetasintheta and costhetacostheta?