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What Are Degrees and Radians?
Angles are measured in two primary units: degrees (°) and radians (rad).
Degrees: A degree is 1⁄360 of a full circle. This system is widely used in everyday contexts (e.g., navigation, construction).
Radians: A radian is the angle subtended at the center of a circle by an arc equal to the radius. One full circle is 2π radians (~6.283 rad). Radians are essential in calculus, physics, and advanced mathematics.
Key Relationship:
- 360° = 2π radians
- 180° = π radians
Why Convert Between Degrees and Radians?
- Math & Science: Calculus, trigonometry, and physics formulas (e.g., angular velocity) require radians.
- Engineering: Rotational systems and signal processing often use radians.
- Programming: Languages like Python and MATLAB default to radians for trigonometric functions.
How to Convert Degrees to Radians
Formula: Radians = Degrees × π / 180
Example: Convert 45° to radians:
45 × π / 180 = π/4 rad ≈ 0.785 rad
Common Conversions:
- 30° = π/6 rad
- 90° = π/2 rad
- 180° = π rad
How to Convert Radians to Degrees
Formula: Degrees = Radians × 180 / π
Example: Convert (3π/4) rad to degrees:
(3π/4) × 180 / π = 135°
Common Conversions:
- π/3 rad = 60°
- π/6 rad = 30°
- 2π rad = 360°
Visualizing the Relationship
Imagine slicing a pizza:
- Degrees: Each slice is labeled from 0° to 360°.
- Radians: Each slice is labeled in terms of π (e.g., π/2, π).
It's the same angle, just different "units"!
Tips for Avoiding Mistakes
- Always include π in degree-to-radian conversions.
- Check that your calculator is in the correct mode (DEG vs. RAD).
- Simplify fractions when possible: π/4 is cleaner than 0.785 rad.
Real-World Applications
- Physics: Angular displacement and motion.
- Computer Graphics: Rotation in 2D/3D rendering.
- Astronomy: Measuring apparent size and motion of celestial objects.
FAQs About Angle Conversions
Q: Why do mathematicians prefer radians?
A: Radians simplify calculus operations, such as derivatives of sine and cosine.
Q: Can I convert negative angles?
A: Yes! For example, -90° = -π/2 radians.
Q: How can I estimate radians without π?
A: Use π ≈ 3.14. So 60° ≈ 1.05 radians.