Question

If the point (-2,3) lies on the terminal side of an angle alpha, find the value of cos alpha

Answer 1

cos a = adjacent / hypotenuse

r = radius

cos a = x / r

To find the radius we use the following

`r = √(x^2 + y^2)`

`r = √(-2^2 + 3^2)`

`r = √(13)`

`\cos \alpha = (x)/(r)`

`\cos \alpha = (-2)/(√(13))`

`\cos \alpha = -(2√(13))/(13)`