High School Math : Understanding Polar Coordinates

Study concepts, example questions & explanations for High School Math

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Example Questions

Example Question #1 : Calculus Ii — Integrals

The polar coordinates of a point are \(\displaystyle \left(2.1, \frac{7\pi }{3}\right )\). Give its \(\displaystyle y\)-coordinate in the rectangular coordinate system (nearest hundredth).

Possible Answers:

\(\displaystyle 4.20\)

\(\displaystyle 1.82\)

\(\displaystyle 1.05\)

\(\displaystyle -1.05\)

\(\displaystyle -1.82\)

Correct answer:

\(\displaystyle 1.82\)

Explanation:

Given the polar coordinates \(\displaystyle (r,\theta )\), the  \(\displaystyle y\)-coordinate is  \(\displaystyle y= r \sin \theta\).  We can find this coordinate by substituting \(\displaystyle r = 2.1, \theta = \frac{7\pi }{3}\):

\(\displaystyle y = r \sin \theta = 2.1 \cdot \sin \frac{7\pi }{3} \approx 2.1 \cdot 0.8660 \approx 1.82\)

Example Question #1 : Understanding Polar Coordinates

The polar coordinates of a point are \(\displaystyle \left(2.1, \frac{7\pi }{3}\right )\). Give its \(\displaystyle x\)-coordinate in the rectangular coordinate system (nearest hundredth).

Possible Answers:

\(\displaystyle -1.05\)

\(\displaystyle 1.82\)

\(\displaystyle -1.82\)

\(\displaystyle 1.05\)

\(\displaystyle 4.20\)

Correct answer:

\(\displaystyle 1.05\)

Explanation:

Given the polar coordinates \(\displaystyle (r,\theta )\), the  \(\displaystyle x\)-coordinate is  \(\displaystyle x= r \cos \theta\). We can find this coordinate by substituting \(\displaystyle r = 2.1, \theta = \frac{7\pi }{3}\):

\(\displaystyle x = r \cos \theta = 2.1 \cdot \cos \frac{7\pi }{3} = 2.1 \cdot 0.5 = 1.05\)

Example Question #1 : Understanding Polar Coordinates

The polar coordinates of a point are \(\displaystyle \left(1.2, \frac{2\pi }{5}\right )\). Give its \(\displaystyle y\)-coordinate in the rectangular coordinate system (nearest hundredth).

Possible Answers:

\(\displaystyle 1.26\)

\(\displaystyle 3.69\)

\(\displaystyle 1.14\)

\(\displaystyle 0.37\)

\(\displaystyle 3.88\)

Correct answer:

\(\displaystyle 1.14\)

Explanation:

Given the polar coordinates \(\displaystyle (r,\theta )\), the  \(\displaystyle y\)-coordinate is  \(\displaystyle y= r \sin \theta\). We can find this coordinate by substituting \(\displaystyle r = 1.2, \theta = \frac{2\pi }{5}\):

\(\displaystyle y = r \cos \theta = 1.2 \cdot \sin \frac{2\pi }{5} \approx 1.2 \cdot 0.9511 \approx 1.14\)

Example Question #4 : Calculus Ii — Integrals

The polar coordinates of a point are \(\displaystyle \left(1.2, \frac{2\pi }{5}\right )\). Give its \(\displaystyle x\)-coordinate in the rectangular coordinate system (nearest hundredth).

Possible Answers:

\(\displaystyle 3.69\)

\(\displaystyle 0.37\)

\(\displaystyle 3.88\)

\(\displaystyle 1.14\)

\(\displaystyle 1.26\)

Correct answer:

\(\displaystyle 0.37\)

Explanation:

Given the polar coordinates \(\displaystyle (r,\theta )\), the  \(\displaystyle x\)-coordinate is  \(\displaystyle x= r \cos \theta\). We can find this coordinate by substituting \(\displaystyle r = 1.2, \theta = \frac{2\pi }{5}\):

\(\displaystyle x = r \cos \theta = 1.2 \cdot \cos \frac{2\pi }{5} \approx 1.2 \cdot 0.3090 \approx 0.37\)

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