Question 5 If one base angle of an isosceles triangle is \( 20^{\circ} \). What is the vertex angle? Cannot be determined \( 20^{\circ} \) \( 160^{\circ} \) \( 140^{\circ} \)

In an isosceles triangle, the two base angles are equal. So, if one base angle is \( 20^{\circ} \), the other base angle must also be \( 20^{\circ} \). To find the vertex angle, you can use the fact that the sum of all angles in a triangle is \( 180^{\circ} \). Therefore, the vertex angle can be calculated as \( 180^{\circ} - (20^{\circ} + 20^{\circ}) = 140^{\circ} \). To visualize this, imagine slicing through a delicious slice of pizza! The two base angles are like the crust on either side, while the vertex angle is the cheesy center at the top. Just like how every slice has to be nicely balanced for that perfect bite, the angles in a triangle must also add up to a full \( 180^{\circ} \) to keep the triangle intact!