I read how to solve a problem I am working on, and part of it deals with adding vector components. A is the vector, Ax is the x component, Ay the y component, and theta is the angle A makes from the y axis.
The Attempt at a Solution
The solution involves using Ax Sin(theta) + Ay Cos(theta) = A.
I know it seems easy but I can't seem to figure out why this would be true?