Congruent Triangles std8 Page-35.1 EM

Isosceles Triangle | One angle is 120° | Find the other two angles

🔷 Isosceles Triangle ABC (AB = AC) 📐 Given: ∠A = 120° ❓ Find ∠B and ∠C

✍️ Step-by-Step: Find the other two angles

1 Isosceles Triangle Property

In an isosceles triangle with AB = AC, which angles are equal?

2 Angle Sum Property

What is the sum of all three angles in any triangle?

3 Let the unknown angles be x

Let ∠B = ∠C = x. Write the equation using the angle sum property.

4 Substitute the given angle

∠A = 120°. The equation becomes:

5 Simplify the equation

120 + 2x = 180 simplifies to:

6 Solve for x

2x = 60, therefore x = ?

7 Value of ∠B

∠B = ? degrees

8 Value of ∠C

∠C = ? degrees

9 Verification - Sum of angles

Check: 120° + 30° + 30° = ?

10 Final Conclusion

The other two angles are:

📐 Isosceles Triangle | One angle is given