Angle Masters
An angle measures 89°. Explain why it is NOT a right angle.
A right angle is exactly 90°.Acute
How many degrees in a right angle?
90
Draw a 45° angle
Acute
Lines that meet to form right angles.
Perpendicular lines
Which is closer to a straight angle: 160° or 80°?
160
One angle is 3 times another angle. Together they make 80°. What are the angles?
20° and 60°.
x+3x=80∘x+3x=80^\circx+3x=80∘
Is 92° acute or obtuse?
Obtuse
Draw an obtuse angle.
Angle more than 90
What angle do perpendicular lines form?
90 degrees
DAILY DOUBLE!!!
True or False: All acute angles are less than 45°
FALSE
A student says:
“Every angle smaller than 100° is acute.”
Why is this wrong?
Right angles are 90° and are not acute.
How many degrees more than 90° is a 125° angle?
35
Draw a straight angle.
Straight line
DAILY DOUBLE!!!
True or False: Perpendicular lines must be horizontal and vertical
FALSE
An angle is:
What could it be?
A right angle (90°)
Two supplementary angles are equal. What is the measure of each angle?
90°.
x+x=180∘x+x=180^\circx+x=180∘
DAILY DOUBLE!!!
A student says 180° is obtuse.
incorrect? 180° is straight.
Draw an angle between 100° and 130°.
DAILY DOUBLE!!!
You draw two perpendicular lines.
Then you tilt the paper sideways.Are the lines still perpendicular?
Yes. They still form 90° angles.
An obtuse angle can never be this type of angle.
Acute angle
Why did the acute angle feel tiny?
Because it was less than 90°!
DAILY DOUBLE!!!
Why did the 89° angle refuse to grow 1 more degree?
Because it didn’t want to be right.
Draw TWO angles that add to 180°
Example: 70° and 110°
What did one perpendicular line say to the other?
“Meet me at 90°!”
A shape has:
Could this shape be a rectangle? Explain.
No. Rectangles have 4 right angles, not a straight angle.