DF ÷ AC = 12 ÷ 4 = 3. This means triangles ABC and DEF are not similar. Angle A and angle D are equal. Angle B and angle E are equal. Angle C and F are equal and are both right angles.

The three angles in a triangle add up to \(180^\circ\). If two of the angles are known then the third can be calculated by following these steps: Add the two known angles together. Subtract the ...