Significance of sector area calculation formula What is the difference between the two L. R's in the two sector area formulas of pie * r * l and (LR) / 2 I'm so anxious

Significance of sector area calculation formula What is the difference between the two L. R's in the two sector area formulas of pie * r * l and (LR) / 2 I'm so anxious

If we calculate the sector area, it should be (LR ^ 2) / 2
L is the radian of the sector and R is the radius
360 degrees are expressed as radians
360 degrees = 2 π
The one upstairs is right
The arc of a sector multiplied by its radius is exactly the arc length of the sector