How do you find the region inside cardioid #r=(alpha)(1+sin(theta)), (alpha)>0#?

Question

3444 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2015-10-16T21:34:43

#A=(3pi alpha^2)/2#

#A=intint rdrd theta#

#A=int_0^(2pi) d theta int_0^(alpha(1+sin theta)) rdr#

#A=int_0^(2pi) d theta r^2/2|_0^(alpha(1+sin theta)) = 1/2 int_0^(2pi) (alpha (1+sin theta))^2 d theta#

#A = alpha^2/2 int_0^(2pi) (1+2sintheta+sin^2theta) d theta#

#A = alpha^2/2 (theta-2costheta+1/2int_0^(2pi) (1-cos2theta) d theta) #

#A = alpha^2/2 (theta-2costheta+theta/2 - 1/4sin2theta) |_0^(2pi) => #

#A=alpha^2/2 (3pi-2+2)#

#A=(3pi alpha^2)/2#