Rule:
The sum of the three interior angles of every triangle is equal to exactly 180°.
Example 1:
Solve for the missing angle.
To solve the problem, solve the equation for angle a.
Subtracting both angles from 180° will give you the answer.
180° - 40° - 60° = 80° *Answer
To check your answer, add all three angles together and verify they add to equal 180°.
Check: 80° + 40° + 60° = 180° ★
Example 2:
Solve for the missing angle.
To solve the problem, solve the equation for angle a.
Subtracting both angles from 180° will give you the answer.
180° - 65° - 20° = 95° *Answer
To check your answer, add all three angles together and verify they add to equal 180°.
Check: 85° + 65° + 20° = 180° ★
Example 3:
Solve for the missing angle.
180° - 50° - 100° = 30° *Answer
Check: 30° + 50° + 100° = 180° ★
Example 4:
Solve for the missing angle.
180° - 50° - 50° = 80° *Answer
Check: 80° + 50° + 50° = 180° ★
Example 5:
Solve for the missing angle.
180° - 85° - 55° = 40° *Answer
Check: 40° + 85° + 55° = 180° ★