In adjoining figure, ABCD is a rectangle. If BP and DQ are perpendiculars on AC from B and D respectively, then is :
(a) AB= CD. Why?
(b)∆BPA=∆DQC. Why?
(c)∆BPA =~∆DQC?
(d)BP=DQ. Why?
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CBSE
Mathematics
Grade 7
Congruence of triangles
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ABCD is a rectangle in which DP and BQ are perpendiculars from D and B respectively on diagonal AC.
Show that
(i)ΔADP≅ΔCBQ
(ii)∠ADP=∠CBQ
(iii)DP=BQ
Answer
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Hint: ABCD is rectangle which means its opposite sides are equal. We can prove ΔADP≅ΔCBQ by using AAS criterion according to which if two angles and one side of a triangle are equal to the two angles and one side of another triangle then the triangles are congruent. Then by CPCT we can prove ∠ADP=∠CBQ and side DP=BQ .
Complete step-by-step answer:
Given ABCD is a rectangle then AB=CD and AD=BC
And DP and BQ are perpendiculars from D and B respectively on diagonal AC.
Then ∠P=∠Q=90∘ and two triangles ΔADP and ΔCBQ are formed.
Now we have to prove-
(i)We have to prove that ΔADP and ΔCBQare congruent.
In ΔADP and ΔCBQ ,
∠APD=∠CQB=90∘ (Given)
∠DAP=∠BCQ (Because they are alternate angles)
Since opposite sides of rectangle are equal so we can write,
Side AB=side BC
Hence by Angle-Angle-Side congruence
ΔADP≅ΔCBQ Hence Proved
(ii) We have to prove that∠ADP=∠CBQ
Since we have already proved thatΔADP≅ΔCBQ
We know that corresponding parts of two congruent triangles are always equal.
Then by CPCT (Corresponding Parts of Congruent Triangles)
∠ADP=∠CBQ Hence Proved
(iii)We have to prove that side DP=side BQ
Since we have already proved that ΔADP≅ΔCBQ
We know that corresponding parts of two congruent triangles are always equal.
Then by CPCT (Corresponding Parts of Congruent Triangles)
Side DP=side BQ Hence Proved.
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