Acute Angle

An Acute Angle is an angle that is smaller than a right angle (i.e. less than [math]\displaystyle{ 90^o, \pi/2 }[/math] radians) .

• See: Right Angle, Right Triangle, Pythagorean Theorem.

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References

2015

• (Wikipedia, 2015) ⇒ http://wikipedia.org/wiki/Angle#Types_of_angles
  • QUOTE:
    • Angles smaller than a right angle (less than 90°) are called acute angles ("acute" meaning "sharp").
    • An angle equal to 1/4 turn (90° or [math]\displaystyle{ \pi/2 }[/math] radians) is called a right angle. Two lines that form a right angle are said to be normal, orthogonal, or perpendicular.
    • Angles larger than a right angle and smaller than a straight angle (between 90° and 180°) are called obtuse angles ("obtuse" meaning "blunt").
    • An angle equal to 1/2 turn (180° or [math]\displaystyle{ \pi }[/math] radians) is called a straight angle.
    • Angles larger than a straight angle but less than 1 turn (between 180° and 360°) are called reflex angles.
    • An angle equal to 1 turn (360° or 2π radians) is called a full angle, complete angle, or a perigon.
    • Angles that are not right angles or a multiple of a right angle are called oblique angles.

1999

• (Wolfram Mathworld , 1999) ⇒ http://mathworld.wolfram.com/AcuteAngle.html
  • QUOTE: An angle of less than [math]\displaystyle{ \pi/2 }[/math] radians (90 degrees) is called an acute angle.

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