Angles around a point
sum to 360º
Starter:
These are the angle facts we have learned so far:
Use the degrees at the side to fill in the missing words.
An acute angle is less than _____
An obtuse angle is less than ______ and more than _____
A right angle is _____
A reflex angle is less than ______ and more than ______
Angles on a straight line add up to _______
90°
180°
360°
Answer starter:
These are the angle facts we have learned so far:
Use the degrees at the side to fill in the missing words.
An acute angle is less than __90°___
An obtuse angle is less than __180°_ and more than __90°__
A right angle is _90°_
A reflex angle is less than _360°_ and more than _180°__
Angles on a straight line add up to __180°___
90°
180°
360°
Refresh
Examples:
1) We know one angle is 45°, what is the other angle "a" ?
1) We know one angle is 45°, what is the other angle "a" ?
2) What is angle "b" ?
2) What is angle "b" ?
3) What is angle "e" ?
3) What is angle "e" ?
4) What is angle "x" and the angle “y”?
y
5) What is the sum of the angles x + 70° + y + 84° ?
4) What is angle "x" and the angle “y”?
y
5) What is the sum of the angles x + 70° + y + 84° ?
Angles around the point
Example
Calculate angle “x”
● Go to: https://www.geogebra.org/m/qvQ8pRJC
● Draw the angles: <BCD=96° and <DCA=132°.
● What is the measure of the other angle ACB(x)?
Now we have to apply the angle fact
Now we have to apply the angle fact
What is angle “x”?
What is angle “x”?
What is angle “x”?
What is angle “x”?
What is angle “x”?
What is angle “x”?
Challenge!
Find the value of “x”
Find the value of “x”
Find the value of “x”
Find the value of “x”
Find the value of “x”
Find the value of “x”
Find the size of each of the four angles
Find the size of each of the four angles
Word problems
Word problems
Word problems
Word problems
Three angles fit exactly around a point. The second angle is 20º more
than the first angle. The third angle is twice the size of the second angle.
Find the size of each of the three angles.
Three angles fit exactly around a point. The second angle is 20º more
than the first angle. The third angle is twice the size of the second angle.
Find the size of each of the three angles.
f + s + t = 360°
first angle = f
second angle (s) = f + 20°
third angle (t) = 2 x s = f + 20 + f + 20
f + f + 20 + f + 20 + f + 20 = 360
2nd
angle
3rd
angle
4f + 60° = 360°
-60
-60
4f = 300°
4
4
f = 75°
Exit ticket:
Quiz