$\displaystyle A = \frac{1}{2}\int_{\theta_1}^{\theta_2} r^2 \, d\theta$
Part (a): $r = 2a \cos \theta$
θ |
0° |
30° |
60° |
90° |
120° |
150° |
180° |
r |
2.000a |
1.732a |
1.000a |
0.000a |
-1.000a |
-1.732a |
-2.000a |
θ |
210° |
240° |
270° |
300° |
330° |
360° |
|
r |
-1.732a |
-1.000a |
0.000a |
1.000a |
1.732a |
2.000a |
|
$\displaystyle A = 2 \times \frac{1}{2}\int_0^{\pi/2} (2a \, \cos \theta)^2 \, d\theta$
$\displaystyle A = 4a^2 \int_0^{\pi/2} (\cos \theta)^2 \, d\theta$
$A = 4a^2(\pi / 4)$
$A = \pi a^2$ answer
Part (b): $r = 2a \sin \theta$
θ |
0° |
30° |
60° |
90° |
120° |
150° |
180° |
r |
0.000a |
1.000a |
1.732a |
2.000a |
1.732a |
1.000a |
0.000a |
θ |
210° |
240° |
270° |
300° |
330° |
360° |
|
r |
-1.000a |
-1.732a |
-2.000a |
-1.732a |
-1.000a |
0.000a |
|
$\displaystyle A = 2 \times \frac{1}{2}\int_0^{\pi/2} (2a \, \sin \theta)^2 \, d\theta$
$\displaystyle A = 4a^2 \int_0^{\pi/2} (\sin \theta)^2 \, d\theta$
$A = 4a^2(\pi / 4)$
$A = \pi a^2$ answer