Show that the diagonals of a square are equal and bisect each other at right angles.
Answers
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☘️ Solution :
To prove :
- AC = BD
- ∠1 = ∠2 = ∠3 = ∠4 = 90°
- OA = OC, OB = OD
Proof :
In ∆ABC and ∆ABD
→ AB = AB (common)
→ AD = BC (side of square)
→ ∠A = ∠B [90°]
.°. ∆ABC ≅ ∆ABD (by SAS)
AC = AB [C.P.C.T]
Then,
In ∆AOD and ∆BOC
→ AB = DC (side of square)
→ ∠2 = ∠4 (vertically opposite angles)
→ ∠5 = ∠6 (alternate interior angle)
.°. ∆AOB ≅ ∆BOC (AAS)
OA = OC, OB = OD (C.P.C.T)
Now,
In ∆AOB and ∆BOC
→ OB = OB (common)
→ AB = BC (Side of square)
→ OA = OC (provide above)
.°. ∆AOB ≅ ∆BOC (SSS)
∠1 = ∠2 (C.P.C.T)
→ ∠1 + ∠2 = 180° (linear pair)
→ ∠1 + ∠1 = 180°
→ 2∠1 = 180°
→ ∠1 = 180/2
→ ∠1 = 90°
Similarly, ∠2 = ∠3 = ∠4 = 90°