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Find the area of the region enclosed by the polar curve 
r=1+cos(theta)

Find the area of the region enclosed by the polar curve r=1+cos(θ) r=1+\cos (\theta)

Full solution

Q. Find the area of the region enclosed by the polar curve r=1+cos(θ) r=1+\cos (\theta)
  1. Identify curve type and symmetry: Identify the type of curve and symmetry.\newlineThe curve given is r=1+cos(θ)r = 1 + \cos(\theta). This is a cardioid. Since cos(θ)\cos(\theta) is symmetric about the vertical axis, the curve is symmetric about the θ=0\theta = 0 line.
  2. Set up integral for area: Set up the integral for the area.\newlineThe area AA enclosed by a polar curve from θ=a\theta = a to θ=b\theta = b is given by A=12(r2)dθA = \frac{1}{2} \int (r^2) d\theta. For a full cardioid, integrate from 00 to 2π2\pi.
  3. Substitute curve equation into integral: Substitute the equation of the curve into the integral.\newlineSubstitute r=1+cos(θ)r = 1 + \cos(\theta) into the integral. So, A=1202π(1+cos(θ))2dθA = \frac{1}{2} \int_{0}^{2\pi} (1 + \cos(\theta))^2 \, d\theta.
  4. Expand and simplify integrand: Expand the integrand and simplify.\newline(1+cos(θ))2=1+2cos(θ)+cos2(θ)(1 + \cos(\theta))^2 = 1 + 2\cos(\theta) + \cos^2(\theta). We know the integral of cos(θ)\cos(\theta) over a full period is 00 and the integral of cos2(θ)\cos^2(\theta) over a full period is π\pi. So, A=1202π(1+2cos(θ)+cos2(θ))dθ=12[2π+0+π]A = \frac{1}{2} \int_{0}^{2\pi} (1 + 2\cos(\theta) + \cos^2(\theta)) d\theta = \frac{1}{2} [2\pi + 0 + \pi].
  5. Calculate final area: Calculate the final area. \newlineA=12[2π+π]=12[3π]=3π2A = \frac{1}{2} [2\pi + \pi] = \frac{1}{2} [3\pi] = \frac{3\pi}{2}.

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