Acute angle
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An acute angle ("acute" meaning "small") is an angle smaller than a right angle. The range of an acute angle is between 0 and 90 degrees, or between 0 and [math]\displaystyle{ \frac{\pi}{2} }[/math] radians. Angles larger than a right angle (90 degrees) are called obtuse. They are found exclusively in Quadrant I or a graph, due to the terminal arm not being able to leave this Quadrant without becoming too large.
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Acute Angle Media
A green angle formed by two red rays on the Cartesian coordinate system
Angles A and B are a pair of vertical angles; angles C and D are a pair of vertical angles. Hatch marks are used here to show angle equality.
Angles A and B are adjacent.
The complementary angles a and b (b is the complement of a, and a is the complement of b.)
The angles a and b are supplementary angles.
Angles AOB and COD are conjugate as they form a complete angle. Considering magnitudes, 45° + 315° = 360°.
Internal and external angles
The measure of angle θ is sr radians.
Definition of 1 radian
Measuring from the x-axis, angles on the unit circle count as positive in the counterclockwise direction, and negative in the clockwise direction.
