The angle is 45 degrees. 2 sides of the triangle is 3 feet long. How long is the third side?

Since two sides are three feet you have an isosceles triangle (two sides the same length). But you don't say if you have ONE 45° angle between the two 3 foot sides OR 45° angles on the other two corners.

This leaves two DIFFERENT possibilities. It could be an isosceles right triangle with one 90° angle and two 45° angles OR an isosceles triangle with only one 45° angle and two 67 1/2° angles

The hypotenuse of an isosceles right triangle ( 45 X 45 X 90) is 1.414 times the length of either of the remaining legs. 3 * 1.414 = 4.243

The short leg of a 22 1/2° and 67 1/2° right triangle is 0.383 (sin22°) times the hypotenuse. 3 * 0.383 = 1.148. But Your triangle (if 45 X 67.5 X 67.5) is the same as two of these together so 2 * 1.148 = 2.296

RobertVA,
Thanks for the answer and I apologise for not being clear on the questuion. This was the scenerio I was looking for. But Your triangle (if 45 X 67.5 X 67.5) is the same as two of these together so 2 * 1.148 = 2.296

I am designing a flower bed around a tree. The tree is 3 feet in diameter. I am making the Diameter of the bed 6 feet. Dividing that circle in 8 parts make eaxh angle from the center at 45 degrees. As you pointed out to me that leaves 67.5 and 67.5 for the other t andles, since I don't have curved boards for the perimeter. I needed to know how long the 8 side pieces would be. You solved it for me. Thanks again
Beau