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If triangleABC cong triangle FDE , AB = ...

If `triangleABC cong triangle FDE , AB = 5 cm , angleB = 40^(@) ,angle A = 80^(@)` Then which of the following is correct ?

A

DF = 5 cm , `angleF = 60^(@`

B

DF = 5 cm ,`angleE = 60^(@)`

C

DF = 5 cm , `angle C = 60 ^(@)`

D

Both (B) and ( C)

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem step by step, we will analyze the information given about triangles ABC and FDE, which are congruent. ### Step 1: Understand the Given Information We are given: - Triangle ABC is congruent to triangle FDE. - \( AB = 5 \, \text{cm} \) - \( \angle B = 40^\circ \) - \( \angle A = 80^\circ \) ### Step 2: Identify Corresponding Parts Since the triangles are congruent, we can use the property of Corresponding Parts of Congruent Triangles (CPCT). This means: - \( AB = FD \) - \( \angle A = \angle F \) - \( \angle B = \angle D \) - \( \angle C = \angle E \) ### Step 3: Calculate the Remaining Angle in Triangle ABC We can find \( \angle C \) using the angle sum property of triangles, which states that the sum of the angles in a triangle is \( 180^\circ \). \[ \angle A + \angle B + \angle C = 180^\circ \] Substituting the known values: \[ 80^\circ + 40^\circ + \angle C = 180^\circ \] \[ 120^\circ + \angle C = 180^\circ \] \[ \angle C = 180^\circ - 120^\circ = 60^\circ \] ### Step 4: Find Corresponding Angles in Triangle FDE Since the triangles are congruent, we have: - \( \angle F = \angle A = 80^\circ \) - \( \angle D = \angle B = 40^\circ \) - \( \angle E = \angle C = 60^\circ \) ### Step 5: Verify the Lengths From the congruence: - Since \( AB = 5 \, \text{cm} \), it follows that \( FD = 5 \, \text{cm} \). ### Step 6: Analyze the Options Now, we check the options provided: 1. \( DF = 5 \, \text{cm} \) and \( \angle F = 60^\circ \) (Incorrect, \( \angle F = 80^\circ \)) 2. \( DF = 5 \, \text{cm} \) and \( \angle E = 60^\circ \) (Correct) 3. \( DF = 5 \, \text{cm} \) and \( \angle C = 60^\circ \) (Correct) 4. Both B and C (Correct) ### Final Answer Thus, the correct answer is option D: Both B and C. ---
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