Triangles ABC and DEF: angle A = angle D = 50, angle B = angle E =…

Step by step, with the reason for every step · Congruent triangles · Geometry

Step by step

Question: which rule shows that triangles ABC and DEF are congruent?

Congruent means the same shape and the same size.

One fits exactly on top of the other.

The order of the letters shows which corners match: A with D, B with E, C with F.

DEF is turned over.

That does not matter.

Angle A and angle D are both 50°: a pair of equal angles.

A for angle.

angle A = angle D = 50° A

Angle B and angle E are both 60°: a pair of equal angles.

A for angle.

angle B = angle E = 60° A

Angle C and angle F are both 70°: a pair of equal angles.

A for angle.

angle C = angle F = 70° A

All three pairs are angles.

Angle, angle, angle: A A A.

angle A, angle B, angle C

Careful: A A A is not a rule.

The angles fix the shape, not the size.

DEF can be a bigger copy.

AAA → not a rule

So we cannot tell if they are congruent.

There is no answer from these facts.

Let's look back.

First: match the parts.

Last: find the rule.

Answer

AAA → not a rule