Thank you all, I'm glad you appreciate the explanation. I'm an engineer so figuring angles and lengths comes easier to me than some of the other parts of sewing. I'm hand appliquéing the plates down and my stitches look like chicken scratch on the back!
Originally Posted by jeanharville
How did you figure that you needed a 105 degree angle.
Each petal covers 30 degrees of the circle, which you can imagine might be 15 degrees on each half, away from the center. A square angle is 90 degrees and the petal sides are each 90 + 15 = 105 degrees.