1. Triangle sum property

2. Triangle Sum Property Theorem
The sum of the measures of the interior angles of a triangle is 180o. 3 2 1
∠1 + ∠2 + ∠3 = 180°

3. 60º 90º 30º 180º Property of triangles
Can we draw a triangle with angles 600, 900 and 300
We know that the sum of the measures of the interior angles of a triangle is 180o.
Sum of 3 angles are
60º
90º
Since sum of 3 angles is equal to 180, triangle can be formed using the given angles.
30º +
180º

4. 70º 70º 70º 210º Property of triangles
Can we draw a triangle with angles 700, 700 and 700
We know that the sum of the measures of the interior angles of a triangle is 180o.
Sum of 3 angles are
70º
Since sum of 3 angles is not equal to 180, triangle cannot be formed using
the given angles.
70º
70º +
210º

5. What is the missing angle?
We know that the sum of angles in a triangle is 180º
Missing angle = sum of other two angle
Missing angle = 180º - 140º = 40º
Sum of other two angle is
70º ?
70º +
70º
140º
70º

6. 90º 30º ? 120º 30º 90º What is the missing angle? +
We know that the sum of angles in a triangle is 180º
Missing angle = sum of other two angle
Missing angle = 180º - 120º = 60º
Sum of other two angle is
90º
30º
90º ? +
30º
120º

7. Find all the angle measures
Solution
We know that sum of angles in a triangle is 180
35x + 45x + 10x = 180
90x = 180
(dividing 90 on both sides)
45x
10x
35x
Angle 1 = 35x = 35 x 2 =70
Angle 2 = 45x = 45 x 2 =90
Angle 3 = 10x = 10 x 2 =20
Ans:- The three angles are 700 , 900 , 200

8. Find the missing angles.
Solution
We know that sum of angles in a triangle is 180
2x + x = 180
2x + x = (subtracting 90 on both sides)
2x + x = 90
3x = 90
(dividing 3 on both sides)
x = 30
Angle 1 = 2x = 2 x 30 =60
Angle 2 = x = 30
Ans:- The three angles are 600 , 300 , 900

9. Three angles of a triangle are xº, x+10º and x+20º, Find x
Solution
We know that sum of angles in a triangle is 180
x + (x + 10) + (x + 20) = 180
x + x + x = 180
3x = 180
3x = (subtracting 30 on both sides)
3x =150
(dividing 3 on both sides)
x = 50

10. Try These:
Can we draw a triangle using the given angles?
80O , 60O , 70O
Find the third angle, given two angles of triangle: 50O , 90O
Find the value of x, if three angles of a triangle are
2x, 3x, x