Measurements of Common Angles/Acute Angle
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Theorem
An acute angle measures $\theta$, where:
- $0 \degrees < \theta < 90 \degrees$
or:
- $0 < \theta < \dfrac \pi 2$
Proof
An acute angle is defined to be an angle whose measure is between that of a zero angle and a right angle.
A zero angle measures $0$ by definition, and a right angle measures $90 \degrees$ or $\dfrac \pi 2$.
Hence the result.
$\blacksquare$
Sources
- 1998: David Nelson: The Penguin Dictionary of Mathematics (2nd ed.) ... (previous) ... (next): angle
- 2008: David Nelson: The Penguin Dictionary of Mathematics (4th ed.) ... (previous) ... (next): angle