Math with Mr. J: Finding Missing Angles in Triangles

Key Concepts

• Triangle Angle Sum Property: The sum of the angles in a triangle is always 180 degrees, regardless of the triangle's shape or classification.
• Magic Number for Triangles: 180 degrees is the total of all three interior angles in any triangle.

Steps to Find Missing Angles

1. Identify Given Angles: Look at the triangle and identify the angles that are provided.
2. Add Known Angles: Add the measures of the given angles.
3. Subtract from 180 Degrees: Subtract the sum of the known angles from 180 degrees to find the measure of the missing angle.

Example Problems

Example 1

• Given Angles: 75 degrees, 35 degrees
• Calculate:
  • Sum of given angles: 75 + 35 = 110 degrees
  • Subtract from 180: 180 - 110 = 70 degrees
• Missing Angle (X): 70 degrees
• Verification: 70 + 75 + 35 = 180 degrees

Example 2

• Given Angles: 50 degrees, 100 degrees
• Calculate:
  • Sum of given angles: 50 + 100 = 150 degrees
  • Subtract from 180: 180 - 150 = 30 degrees
• Missing Angle (X): 30 degrees
• Verification: 30 + 50 + 100 = 180 degrees

Summary

• To find a missing angle in a triangle, sum the known angles and subtract from 180 degrees.
• Always verify by adding all angles to ensure they total 180 degrees, confirming the correctness of your solution.

End of lecture notes. Remember to practice finding missing angles with various examples!