Answer:
1, 2, 4, 5
Explanation:
You want triangles congruent to triangle 4.
Congruence
In this exercise, we can determine congruence using SSS congruence: the lengths of the sides in congruent triangles will match. (The order of appearance of the side lengths as you go around the triangle is irrelevant.)
Triangle 4
The lengths of the sides are ...
- diagonal of 4×2 rectangle
- 5 grid squares
- diagonal of 4×3 rectangle
Looking at the other triangles, we see side lengths of ...
Triangle 1
All side lengths match: congruent to 4.
Triangle 2
All side lengths match: congruent to 4.
Triangle 3
One side is 6 grid squares: not congruent.
Triangle 5
All side lengths match: congruent to 4.
Triangle 6
One side is 6 grid squares: not congruent.
Triangle 7
One side is the diagonal of a 3×2 rectangle: not congruent.
Triangle 8
One side is the diagonal of a 4×1 rectangle: not congruent.
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Additional comment
Triangles 3 and 6 are congruent to each other, but not to triangle 4.