Vector Projection Homework: Figuring Out the Angle

[iflabs]

Homework Statement

I have a vector diagram attached below. Vector A is perpendicular to vector B.

How do you figure out what angle to use in order to project vector A onto the x and y axis?

Homework Equations

A dot B = ABcos(angle)

The Attempt at a Solution

180-30-90 = 60?

 

[HallsofIvy]

Exactly right- though you don't really need the "180" and "90". Extend A back to line C and you will see that the three lines form a right triangle. That tells you that the angle A makes with C is the complement of 30 degeres, 60. And, since C is parallel with the x-axis, extending it further shows (corresponding angles in parallel lines) that it makes the same angle with the x-axis.