The center angle of the sector circle is 90 degrees. What is R + L divided by L?

The center angle of the sector circle is 90 degrees. What is R + L divided by L?

∵ arc length = (90 × π × R) △ 180,
∴r+l=[r+（π×r）÷2]÷[（π×r）/2]=（πr+2r)/πr=1+2、π

What is the sector center angle
Do a topic that the center angle of the fan is 90 degrees, but the picture is clearly a semicircle

That's his mistake in the title

Sector center angle
In the sector of area s, the center angle is a, the radius is r, and when the sector perimeter is the smallest, what are a and R respectively?

The perimeter is 2R + ar... The area is 1 / 2R ^ 2A = s, i.e. a = 2S / R ^ 2, so when the perimeter is 2R + 2S / R, the maximum is r = sqrt (s), a = 2