math
posted by Rose .
A plane leaves hamilton and flies due east 75 km at the same time a second plane flies in a direction of 40degress southeast for 120 km how far apart are the planes when they reach their destination.
I say the calculation is 75^2+120^22(75)(120)cos40
the book says to use cos 45 is this a typo or am I missing something???

I agree with you,
don't see how the angle of 45° can enter the picture.
I can see confusion about their "direction of 40° southeast"
 it could mean E 40° S, or
 it could mean S 40° E to some people.
but even with those interpretations the other angle would be 50°