Exercise · ZW-POLAR-COORDINATES-006 · ★☆☆ Basic
Find the area of the half-disc \(0\le r\le3\), \(0\le\theta\le\pi\).
Choose one option.
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- A. \(\tfrac{9\pi}{2}\)
Explanation
\(\int_0^\pi\!\int_0^3 r\,dr\,d\theta=\tfrac92\cdot\pi=\tfrac{9\pi}{2}\), half of \(\pi\cdot3^2\).
Review the concept: Polar coordinates
Polar coordinates locate a point of the plane by its distance \(r\) from the origin and the angle \(\theta\) its radius makes with the positive \(x\)-axis.
\[x=r\cos\theta,\quad y=r\sin\theta\]
More practice problems: polar coordinates
- ZW-POLAR-COORDINATES-001 Find the x-coordinate of the point with r=4 and θ=tfracπ3.
- ZW-POLAR-COORDINATES-002 The Cartesian point (-1,1) written in polar form with r>0 and 0≤θ<2π is:
- ZW-POLAR-COORDINATES-003 The circle x^2+y^2=9 is written in polar coordinates as:
- ZW-POLAR-COORDINATES-004 Using dA=r dr dθ, compute the area of the disc of radius 2: ∫_0^2π\!∫_0^2 r dr dθ.
- ZW-POLAR-COORDINATES-005 Compute iint_D (x^2+y^2) dA, where D is the unit disc x^2+y^2≤1.
- ZW-POLAR-COORDINATES-007 The polar curve r=2cos θ is:
- ZW-POLAR-COORDINATES-008 Compute iint_D x dA, with D the quarter disc of radius 2 in the first quadrant.
- ZW-POLAR-COORDINATES-009 Integrating e^-(x^2+y^2) over the disc of radius a and letting a→∞, the value of iint_ℝ^2e^-(x^2+y^…