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In the figure below, ABC DEF, A = 45°, C = 85°. Find the measures of D and E.

Mathematics

ScanSolve AI Answer

Answer

c

∠D=45∘,∠E=50∘\angle D = 45^\circ, \angle E = 50^\circ

Step-by-step solution

3 steps

Part a

If two triangles are congruent, then they have exactly same shape and size (True or False).

  • True. Congruent triangles are defined as having the same shape and size.

Part b

Any two equilateral triangles are congruent (True or False).

  • False. While all equilateral triangles have the same shape (all angles are 60∘60^\circ), their sizes can differ. For example, an equilateral triangle with side length 2 cm is not congruent to an equilateral triangle with side length 5 cm.

Part c

∠D=45∘,∠E=50∘\angle D = 45^\circ, \angle E = 50^\circ

In the figure below, △ABC≡△DEF\triangle ABC \equiv \triangle DEF, ∠A=45∘\angle A = 45^\circ, ∠C=85∘\angle C = 85^\circ. Find the measures of ∠D\angle D and ∠E\angle E.

  1. Use the property of congruent triangles to find ∠D\angle D.

    Since △ABC≡△DEF\triangle ABC \equiv \triangle DEF, their corresponding angles are equal.
    Therefore, ∠A=∠D\angle A = \angle D.
    Given ∠A=45∘\angle A = 45^\circ.

    ∠D=45∘\angle D = 45^\circ
  2. Find ∠B\angle B in △ABC\triangle ABC.

    The sum of angles in a triangle is 180∘180^\circ.

    ∠A+∠B+∠C=180∘\angle A + \angle B + \angle C = 180^\circ 45∘+∠B+85∘=180∘45^\circ + \angle B + 85^\circ = 180^\circ 130∘+∠B=180∘130^\circ + \angle B = 180^\circ ∠B=180∘−130∘\angle B = 180^\circ - 130^\circ ∠B=50∘\angle B = 50^\circ
  3. Use the property of congruent triangles to find ∠E\angle E.

    Since △ABC≡△DEF\triangle ABC \equiv \triangle DEF, their corresponding angles are equal.
    Therefore, ∠B=∠E\angle B = \angle E.
    From Step 2, ∠B=50∘\angle B = 50^\circ.

    ∠E=50∘\angle E = 50^\circ

    The measures are: ∠D=45∘,∠E=50∘\boxed{\angle D = 45^\circ, \angle E = 50^\circ}

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