Angles in Triangles Flashcards

All 6 cards in this deck

What do the angles in a triangle add up to?

$180^\circ$

What is the size of each angle in an equilateral triangle?

$60^\circ$

What is the angle property of an isosceles triangle?

The two angles opposite the two equal sides are equal.

What are the steps to find the base angles of an isosceles triangle?

e.g. the angle between the two equal sides is $40^\circ$

1. Subtract from $180$: $180 - 40 = 140$
2. Halve it (the two base angles are equal): $140 \div 2 = 70$, so each base angle is $70^\circ$

What is the exterior angle of a triangle equal to?

e.g. the two interior angles at the other two vertices are $50^\circ$ and $60^\circ$

The sum of the two opposite interior angles.
e.g. exterior angle $= 50 + 60 = 110^\circ$

True or false? In an isosceles triangle the equal angles are always the two angles at the bottom of the diagram.

False. The equal angles are the ones opposite the two equal sides, wherever they appear.