🔺 Angles & Triangles

Question 1

Why do the angles in a triangle add up to 180°?

Answer 1

Imagine you draw a straight line (180°). Now put a triangle under it and extend one side. The inside angles of the triangle line up perfectly to form that straight line. Since a line = 180°, all triangle angles = 180°.

Question 2

What is an exterior angle of a triangle, and why is it special?

Answer 2

An exterior angle is formed when you extend one side of a triangle. The cool rule: that exterior angle = the sum of the two opposite inside angles. Why? Because the exterior + the inside angle next to it = 180°. Subtract the adjacent inside angle, and you’re left with the other two.

Question 3

Why are base angles of an isosceles triangle equal?

Answer 3

If two sides are equal, the triangle is symmetric. Fold it in half along the “middle line” → one side perfectly matches the other. That means the angles opposite those equal sides must also be equal.

Question 4

What happens when a line crosses two parallel lines (transversal)?

Answer 4

Think of railroad tracks with a stick crossing.

Corresponding angles: same “corner” on each intersection = equal.
Alternate interior angles: inside the tracks, opposite sides = equal.
Same-side interior angles: both inside, same side = add to 180°.