The radius of the larger arc after expansion is r, and the included angle between the two sides after expansion (that is, the central angle of the sector) is degrees, that is, the included angle between the two sides you want.

Pi in the title is pi=3. 14 159. .......

Find the length of the hypotenuse of this bucket first (usually called frustum in mathematics).

Pythagorean theorem is: l 2 = [(8-5)/2] 2+7 2.

L= get the root number 205/2.

L=7. 159。

A/360*2*pi*R=pi*8

A/360*2*pi*(R- 1)=pi*5

Upper and lower segmentation

R/(R-L)=8/5

R=8L/3= 19. 1m, so what's next?

You can work out r-l.

Substitute r into A/360*2*pi*R=pi*8 again.

Get: a = 75.43.

However, my suggestion is that if you are in actual production, it is suggested that the included angle must be larger, otherwise you will find that there is no extra hypotenuse to overlap when rolling. Also, if you want to make the upper and lower back covers, you should expand the value of L a little, but this is uncertain. You can use different processes. Usually this is a sheet metal work, but the area is a bit large.