15 degree triangle

Check out this fun problem at the math challenges blog. I picked it in honor of what we’re doing in Precalculus right now, since it has a trigonometric flavor. Don’t look at the answer until you’ve tried it! In fact, after looking at the answer, I found I had done it a different way. So let your creativity run wild. I’d love to see your proof, if you figure it out. And if you want a hint, come see me or email me.