In isosceles triangle DEF, DE=DF. Which of the following is true?

1) <D is congruent to <E
2) <F is congruent to <E
3) <D is congruent to <F
4) <D is congruent to <E which is congruent to <F

Is the answer (3)?

In triangle ABC, if line AB is congruent to line AC and m<A=70,find m<B.
dOES THE M<b=70?

wdw

For the first question about the isosceles triangle DEF, the correct answer is (1). In an isosceles triangle, the angles opposite the congruent sides are also congruent. Therefore, in triangle DEF, since DE=DF, angle D and angle E are congruent.

For the second question about triangle ABC, we cannot determine if m<B is equal to 70 based on the given information. If line AB is congruent to line AC and m<A=70, it means that angle B and angle C are congruent. However, the lengths of the sides do not provide information about the measure of the angles. We need additional information, such as the angle measures of the other angles in the triangle, to determine the measure of angle B.