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Introduction to Angles
Transcript of Introduction to Angles
Acute Angles are angles less than 90˚
I like to remember this by thinking they are 'small' and 'cute.'
Obtuse Angles are more than 90˚ but less than 180˚
I like to remember this by thinking about the word obtuse and how it can also mean thick.
All About Angles
Right angles are exactly 90˚
You may recall that perpendicular lines create 90˚ angles as well.
Perpendicular lines cross at exactly 90˚
90˚ angles are notated with a box symbol
This video is a fun way to review what we have learned. Feel free to watch it multiple times or revisit the pages in this activity!
Parallel lines never
meet,so they do not
Intersecting lines cross
each other (much like
intersections on roads)
to form angles.
Can you see the obtuse angle?
So, perpendicular lines create 90˚ angles, these are called right angles.
right angle notation
Straight angles are exactly 180˚
"Wow! He did a complete 180!"
When people say this they are referring to a complete change in the opposite direction. Just like these two line segments are pointed in the exact opposite direction.
Reflex angles are over 180˚ but less than 360˚ (or a full circle)
What are you being asked to find?
The reflex angle is always greater than 180˚
The smaller angle can be either obtuse or acute.
The larger angle is the reflex angle.
* Take note that the reflex angle is the larger angle
Two angles are complementary when they add up to 90˚
Two angles are supplementary when they add up to 180˚
Notice how in all of the examples both angles create a perfect right angle!
Notice how in all of the examples both angles create a perfect straight angle!