What is an Angle?
An angle is the figure formed by two rays (the sides of the angle) sharing the same endpoint, called the vertex of the angle.
Types of angles:
What is an Acute Angle? Acute angles are less than 90 degrees, but larger than zero degrees. Subtract degrees from a right, 90 degrees, angle to get an acute angle. You can add 2 or more acute angles to equal a right angle.
What is a Right Angle? A right angle is an angle of exactly 90 degrees
What is a Obtuse Angle? Any angle greater than 90 degrees and smaller than 180 degrees is called an Obtuse Angle.
What is a Straight Angle? A straight angle is only when the degree is exactly 180.
What is a Reflex? A reflex is when the angle was to be grater the 180 degrees and less than 360 degrees.
What is a Full Rotation? When the angle is exactly 360 degrees.
Pairs of Angles
What are Complementary angles? In a right angled triangle, the two non-right angles are complementary, because in a triangle the three angles add to 180 degrees, and 90 degrees.
What are Supplementary Angles? Two Angles are Supplementary when they add up to 180 degrees. They don’t have to be next to each other, just as long as the total is 180 degrees. Example: 90 degrees and 90 degrees adds up to 180 degrees.
What are Vertically opposite angles? Vertically Opposite Angles are the angles opposite to each other when two lines cross. Vertical in this case means they share the same Vertex, not the usual meaning of up-down.
What are Parallel Lines? Parallel lines are lines in a plane which do not meet. Two lines in a plane that do not intersect or touch each other at any point are to be parallel.
Angles around a point will always add up to 360 degrees.
The different types of triangles:
A triangle with three equal sides is called an equilateral triangle. When only two of the sides are equal, it is called an isosceles triangle. If none of the sides is the same, the figure is called a scalene triangle. Equilateral triangles have equal angles, each 60 degrees and add up to 180 degrees. Every triangle should have each angle add up to 180 degrees. Example: A triangle with 3 sides each side is 60 degrees and all 3 sides add up to 180 degrees.