Which of the following is equal to `cos theta` ?

Options

A. `(a)/(sqrt(a^(2)+b^(2)))`
B. `(b)/(sqrt(a^(2)+b^(2)))`
C. `(b)/(a)`
D. `(sqrt(a^(2)+b^(2)))/(b)`

Answer

A

Explanation

For any point `(u, upsilon), cos theta = (r )/(upsilon)`, where r is the distance from `(u, upsilon)` to the origin. See the drawing below .

In this question, the distance r from point (a, b) to the origin is `sqrt(a^(2)+b^(2))`. So `cos theta = (sqrt(a^(2)+b^(2)))/(b)`.