Show that the diagonals of a quadrilateral are equal and bisect each other at right angles, then it is a square.
Answers
Given,
Diagonals are equal
Diagonals are equalAC=BD .......(1)
Diagonals are equalAC=BD .......(1)and the diagonals bisect each other at right angles
Diagonals are equalAC=BD .......(1)and the diagonals bisect each other at right anglesOA=OC;OB=OD ...... (2)
Diagonals are equalAC=BD .......(1)and the diagonals bisect each other at right anglesOA=OC;OB=OD ...... (2)∠AOB= ∠BOC= ∠COD= ∠AOD= 90
Diagonals are equalAC=BD .......(1)and the diagonals bisect each other at right anglesOA=OC;OB=OD ...... (2)∠AOB= ∠BOC= ∠COD= ∠AOD= 90 0
Diagonals are equalAC=BD .......(1)and the diagonals bisect each other at right anglesOA=OC;OB=OD ...... (2)∠AOB= ∠BOC= ∠COD= ∠AOD= 90 0 ..........(3)
Proof:
Proof:Consider △AOB and △COB
Proof:Consider △AOB and △COBOA=OC ....[from (2)]
Proof:Consider △AOB and △COBOA=OC ....[from (2)]∠AOB= ∠COB
Proof:Consider △AOB and △COBOA=OC ....[from (2)]∠AOB= ∠COBOB is the common side
Proof:Consider △AOB and △COBOA=OC ....[from (2)]∠AOB= ∠COBOB is the common sideTherefore,
Proof:Consider △AOB and △COBOA=OC ....[from (2)]∠AOB= ∠COBOB is the common sideTherefore,△AOB≅ △COB
Proof:Consider △AOB and △COBOA=OC ....[from (2)]∠AOB= ∠COBOB is the common sideTherefore,△AOB≅ △COBFrom SAS criteria, AB=CB
Proof:Consider △AOB and △COBOA=OC ....[from (2)]∠AOB= ∠COBOB is the common sideTherefore,△AOB≅ △COBFrom SAS criteria, AB=CBSimilarly, we prove
Proof:Consider △AOB and △COBOA=OC ....[from (2)]∠AOB= ∠COBOB is the common sideTherefore,△AOB≅ △COBFrom SAS criteria, AB=CBSimilarly, we prove△AOB≅ △DOA, so AB=AD
Proof:Consider △AOB and △COBOA=OC ....[from (2)]∠AOB= ∠COBOB is the common sideTherefore,△AOB≅ △COBFrom SAS criteria, AB=CBSimilarly, we prove△AOB≅ △DOA, so AB=AD△BOC≅ △COD, so CB=DC
Proof:Consider △AOB and △COBOA=OC ....[from (2)]∠AOB= ∠COBOB is the common sideTherefore,△AOB≅ △COBFrom SAS criteria, AB=CBSimilarly, we prove△AOB≅ △DOA, so AB=AD△BOC≅ △COD, so CB=DCSo, AB=AD=CB=DC ....(4)
....(4)So, in quadrilateral ABCD, both pairs of opposite sides are equal, hence ABCD is parallelogram.
In △ABC and △DCB
In △ABC and △DCBAC=BD ...(from (1))
In △ABC and △DCBAC=BD ...(from (1))AB=DC ...(from $$(4)$$)
In △ABC and △DCBAC=BD ...(from (1))AB=DC ...(from $$(4)$$)BC is the common side
In △ABC and △DCBAC=BD ...(from (1))AB=DC ...(from $$(4)$$)BC is the common side△ABC≅ △DCB
In △ABC and △DCBAC=BD ...(from (1))AB=DC ...(from $$(4)$$)BC is the common side△ABC≅ △DCBSo, from SSS criteria, ∠ABC= ∠DCB
In △ABC and △DCBAC=BD ...(from (1))AB=DC ...(from $$(4)$$)BC is the common side△ABC≅ △DCBSo, from SSS criteria, ∠ABC= ∠DCBNow,
In △ABC and △DCBAC=BD ...(from (1))AB=DC ...(from $$(4)$$)BC is the common side△ABC≅ △DCBSo, from SSS criteria, ∠ABC= ∠DCBNow,AB∥CD,BC is the tansversal
In △ABC and △DCBAC=BD ...(from (1))AB=DC ...(from $$(4)$$)BC is the common side△ABC≅ △DCBSo, from SSS criteria, ∠ABC= ∠DCBNow,AB∥CD,BC is the tansversal∠B+∠C= 180
In △ABC and △DCBAC=BD ...(from (1))AB=DC ...(from $$(4)$$)BC is the common side△ABC≅ △DCBSo, from SSS criteria, ∠ABC= ∠DCBNow,AB∥CD,BC is the tansversal∠B+∠C= 180 0
In △ABC and △DCBAC=BD ...(from (1))AB=DC ...(from $$(4)$$)BC is the common side△ABC≅ △DCBSo, from SSS criteria, ∠ABC= ∠DCBNow,AB∥CD,BC is the tansversal∠B+∠C= 180 0
In △ABC and △DCBAC=BD ...(from (1))AB=DC ...(from $$(4)$$)BC is the common side△ABC≅ △DCBSo, from SSS criteria, ∠ABC= ∠DCBNow,AB∥CD,BC is the tansversal∠B+∠C= 180 0 ∠B+∠B= 180
In △ABC and △DCBAC=BD ...(from (1))AB=DC ...(from $$(4)$$)BC is the common side△ABC≅ △DCBSo, from SSS criteria, ∠ABC= ∠DCBNow,AB∥CD,BC is the tansversal∠B+∠C= 180 0 ∠B+∠B= 180 0
In △ABC and △DCBAC=BD ...(from (1))AB=DC ...(from $$(4)$$)BC is the common side△ABC≅ △DCBSo, from SSS criteria, ∠ABC= ∠DCBNow,AB∥CD,BC is the tansversal∠B+∠C= 180 0 ∠B+∠B= 180 0
In △ABC and △DCBAC=BD ...(from (1))AB=DC ...(from $$(4)$$)BC is the common side△ABC≅ △DCBSo, from SSS criteria, ∠ABC= ∠DCBNow,AB∥CD,BC is the tansversal∠B+∠C= 180 0 ∠B+∠B= 180 0 ∠B= 90
In △ABC and △DCBAC=BD ...(from (1))AB=DC ...(from $$(4)$$)BC is the common side△ABC≅ △DCBSo, from SSS criteria, ∠ABC= ∠DCBNow,AB∥CD,BC is the tansversal∠B+∠C= 180 0 ∠B+∠B= 180 0 ∠B= 90 0
In △ABC and △DCBAC=BD ...(from (1))AB=DC ...(from $$(4)$$)BC is the common side△ABC≅ △DCBSo, from SSS criteria, ∠ABC= ∠DCBNow,AB∥CD,BC is the tansversal∠B+∠C= 180 0 ∠B+∠B= 180 0 ∠B= 90 0
In △ABC and △DCBAC=BD ...(from (1))AB=DC ...(from $$(4)$$)BC is the common side△ABC≅ △DCBSo, from SSS criteria, ∠ABC= ∠DCBNow,AB∥CD,BC is the tansversal∠B+∠C= 180 0 ∠B+∠B= 180 0 ∠B= 90 0 Hence, ABCD is a parallelogram with all sides equal and one angle is 90
0
So,ABCD is a square.
Hence proved.
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