Question

Difficulty: EasyUnit Circle and Angle Measures (Radians and Degrees)

A central angle of a circle measures 315315^\circ. What is the radian measure of this angle?

  1. A
    47π\frac{4}{7\pi}
  2. B
    4π7\frac{4\pi}{7}
  3. C
    2π3\frac{2\pi}{3}
  4. D
    7π8\frac{7\pi}{8}
  5. 7π4\frac{7\pi}{4}Answer

Answer

7π4\frac{7\pi}{4}
To convert degrees to radians, multiply the degree measure by π180\frac{\pi}{180^\circ}. Multiplying 315315^\circ by π180\frac{\pi}{180^\circ} gives 315π180\frac{315\pi}{180}. Simplifying the fraction by dividing the numerator and the denominator by their greatest common divisor, 45, results in 7π4\frac{7\pi}{4} radians.

Step-by-Step Solution

1
Set up the conversion from degrees to radians.
Multiply 315315^\circ by the conversion factor π180\frac{\pi}{180^\circ}.
The conversion factor from degrees to radians is π180\frac{\pi}{180^\circ} because a straight angle of 180180^\circ is equivalent to π\pi radians.
2
Perform the multiplication and simplify the resulting fraction.
315×π180=315π180=7π4315 \times \frac{\pi}{180} = \frac{315\pi}{180} = \frac{7\pi}{4}.
Dividing both the numerator 315 and the denominator 180 by their greatest common divisor, 45, yields the simplified fraction 74\frac{7}{4}.

Key Concept

To convert an angle from degrees to radians, multiply the degree measure by π180\frac{\pi}{180^\circ} and simplify the resulting fraction.
Estimated Time:45s
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