Interior and Exterior Angles of Triangles

Right Angle A right angle has a measurement of 90 degrees

Straight Angle A straight angle Has a measurement Of 180 degrees

Acute Angle An acute angle has A measurement of Less than 90 degrees

Obtuse Angle An obtuse angle has A measurement of More than 90 degrees

Complimentary Angles Their measures add up to exactly 90 degrees

Supplementary Angles Their measures add up to exactly 180 degrees

Finding Missing Angles 25º x x + 25 = 90

45ºx x + 45 = 180

Finding the complimentary and supplementary angles 30° Complimentary: 30 + x = 90 Supplementary: 30 + x = 180 The complimentary angle is 60⁰ and the supplementary angle is 150⁰

65° The complimentary angle is ___⁰ and the supplementary angle is _____⁰

105° In this case there is no complimentary angle, only a supplementary angle. Why?

Triangles

Finding a Missing Angle The sum of all angles in a triangle is 180 degrees. You should remember that from last year, but why?

Let’s Look at it Three Ways Cutting off the angles I cut off angles 2 and 3 and lined them up to form a straight line

Rotating the Triangle In this picture angles 1, 2, and 3 combine to make a straight line of 180⁰

Using parallel lines and transversals Angle 2 by vertical angles, angles 1 and 3 by complimentary angles

Putting it into action

Your Turn

Finding an exterior angle -Create a straight line to solve 80⁰ + x⁰ make up the straight line. The 55⁰ and 45⁰ have nothing to do with it.

Your Turn 35° 55°

60º x

145º x y

Find all the missing angles 85° 154°

Closure Two angles that are supplementary add up to ______

Closure Two angles that are complimentary add up to ______

Closure A straight line is _______

Closure The sum of all angles in a triangle equals:

Closure: With a partner find all the missing angles 125° 168°