Chapter 5: Problem 2
Indicate each angle on a circle: \(30^{\circ}, 315^{\circ},-135^{\circ}, 80^{\circ}, \frac{7 \pi}{6}, \frac{3 \pi}{4}\)
Short Answer
Expert verified
Angles are: 30° (Q1), 80° (Q1), 315° (Q4), -135° (Q3), \(\frac{7\pi}{6}\): 210° (Q3), \(\frac{3\pi}{4}\): 135° (Q2).
Step by step solution
01
Identifying Positive Angles
We first focus on the angles given in degrees that are positive:
- For 30°, it is located in the first quadrant.
- For 80°, it is also located in the first quadrant.
- For 315°, it is in the fourth quadrant, which is 45° less than a full circle (360° - 315° = 45°). Identify these angles on the circumference of the circle.
02
Dealing with Negative Angles
Next, we address the negative angle of -135°. Starting from 0° and moving in the clockwise direction (since it's negative), -135° terminates in the third quadrant equivalent to 225° (360° - 135° = 225° if moving counter-clockwise). Identify this angle on the circle.
03
Converting Radian Angles to Degrees
Convert the radian measures to degree measures to locate them on the circle:- For \(\frac{7\pi}{6}\), use the formula \(\text{degrees} = \text{radians} \times \frac{180}{\pi}\) to get 210°.- For \(\frac{3\pi}{4}\), convert to degrees using the same formula to get 135°.
04
Locating Radian Angles on the Circle
Now, using the degree conversions, locate these angles on the circle:- 210° (from \(\frac{7\pi}{6}\)) falls in the third quadrant.- 135° (from \(\frac{3\pi}{4}\)) falls in the second quadrant.
05
Verifying All Angles
Verify that each calculated position for the angles is accurate by cross-referencing with known quadrant locations:- 30° and 80° are in the first quadrant.- 135° (both from the degree measure and \(\frac{3\pi}{4}\)) is in the second quadrant.- 210° (from \(\frac{7\pi}{6}\)) and -135° each align in the third quadrant equivalently.- 315° is in the fourth quadrant. Confirm each position accurately aligns with these descriptions.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Quadrants
When measuring angles on a circle, the circle is divided into four sections known as quadrants. These quadrants help identify the position of angles:
- The first quadrant encompasses angles between 0° and 90°, where both sine and cosine values are positive.
- The second quadrant holds angles from 90° to 180°, where sine is positive, but cosine is negative.
- In the third quadrant, angles range from 180° to 270°, with both sine and cosine values being negative.
- The fourth quadrant contains angles from 270° to 360°, where sine is negative and cosine is positive.
Degree Conversion
Degrees are a common unit of angle measurement. Converting radian angles to degrees is crucial when interpreting standard angle measures. The conversion formula used is:\[ \text{degrees} = \text{radians} \times \frac{180}{\pi} \]This formula helps us translate radians into a more familiar unit:
- For \( \frac{7\pi}{6} \), the angle converts to 210°.
- For \( \frac{3\pi}{4} \), the angle becomes 135°.
Radian Conversion
Radian conversion is an essential skill in trigonometry and involves changing degrees into radians to handle calculations typical in advanced mathematics. To convert degrees to radians, use:\[ \text{radians} = \text{degrees} \times \frac{\pi}{180} \]Radian measures are often used in calculus due to their natural simplification of mathematical analysis. When studying angles:
- Radian values like \( \frac{7\pi}{6} \) translate to circle segments in terms of \(210^{\circ}\).
- Likewise, \( \frac{3\pi}{4} \) corresponds to \(135^{\circ}\).
Trigonometry
Trigonometry is the branch of mathematics that explores the relationships and functions between angles and sides of triangles.
Understanding quadrants and conversions form a base in trigonometry:
- Using sine, cosine, and tangent, trigonometry extends beyond mere planar angles, moving into periodic functions describing waves and oscillatory motions.
- Angular measurements, whether in degree or radian form, help define these trigonometric functions within each quadrant's unique properties.