Area of circle

[FatCat727 No.9685452]

Hi /sci/, could you explain me how to get formula S=π.r^2 by integration in polar coordinate system?

[Anonymous No.9685518]

The angle (θ) goes from 0 to 2pi, and r goes from 0 to r, then you just integrate the usual formula for surface in polar cordinates. /dθ/r×dr, which when you solve you get pi×r^2 I don't know how to use the stupid math thingy to make it look nice so i nust used / for integrals but you should get the point.

[Anonymous No.9685540]

>>9685452
[math]\iint_{0 0}^{2\pi\ R}r\ dr\ d\theta=\pi r^2}[/math]

[Anonymous No.9685543]

>>9685540
Fuc
[math]\iint_{0 0}^{2\pi\ R}r\ dr\ d\theta=\pi r^2[/math]

[Anonymous No.9685547]

>>9685543
If you really wanna be technical, r should be in my bounds of integration and R should be my dummy variable inside the integral and differential.