How Do You Calculate Path-Length Differences in Two-Source Interference?

[aliaze1]

Homework Statement

http://session.masteringphysics.com/problemAsset/1014010/14/1014010E.jpg

What are the path-length differences at Points A, C, and D
(respectively, ΔdA, ΔdC, ΔdD)?

Enter your answers numerically in terms of lambda λ

Homework Equations

Does this require an equation? I figured it was pictorial

http://session.masteringphysics.com/problemAsset/1014010/14/1014010D.jpg

The Attempt at a Solution

I looked at the picture and tried the following, which were all incorrect:

3.5, 2.5, 2
3, 2, 1.5

 

[aliaze1]

got it lol

nevermind, i got it, i used this:

http://session.masteringphysics.com/problemAsset/1014010/14/1014010F.jpg