## Online Course Discussion Forum

### Math II-A Geometry 1.29

Math II-A Geometry 1.29

Given that one of the angles of the triangle with sides (5, 7, 8) is 60°, show that one of the angles of the triangle with sides (3, 5, 7) is 120°. I don't really see how these two triangles are related. I think that the first triangle side with 7 is angle 60°, and 7 on the second triangle is also 120°. I have also tried connecting the two triangles together into a quadrilateral, the same integers sharing a side. I'm wondering if I could get a hint of how to solve this. Thank you.

Re: Math II-A Geometry 1.29

Very good observation that the angle opposite $7$ is $60^\circ$.  Also, great intuition to connect the two triangles sharing the side $7$!  Now, instead of putting the $(3,5,7)$ triangle outside the $(5,7,8)$ triangle, can you put it inside?