Theorem: In a square the diagonals are equal and perpendicular to each other.
Given: A square ABCD. To Prove: AC = BD and AC and BC intersect perpendicularly. Proof: In ADB and BCA AD = BC [ Sides of square are equal] DAB = CBA [Each angle is ] AB = AB [ Common] Therfore DAB CBA [SAS Criteria of Congruence] BD = AC As ABCD is a square Therefore it is a parallelogram. Also diagonals of a parallelogram bisect each other. AO = OC and BO = OD ...................(1) In BOC and COD BO = DO [ From Equation (1)] BC = CD [ Sides of a square] OC = OC [ Common ] Therfore BOC DOC [SSS Criteria of Congruence] [ By CPCT ] ............(2) But [Linear Pair] [Using Eq 2]
Similarly we can prove that Hence Proved that In a square the diagonals are equal and perpendicular to each other. | |
Theorem : If the diagonals of a parallelogram are equal and intersect at right angles, then the parallelogram is a square. | |
Given : ABCD is a parallelogram, such that AC = BD and AC BD To Prove: ABCD is a square Proof: In AOB and COB AO = OC [ Diagonals of parallelogram bisect each other] BO = OB [ Common] AOB = COB [ Each as AC BD] Therefore AOB COB [ SAS Criteria of Congurence] AB = BC [CPCT] As ABCD is a IIgm and the adjacent sides are equal AB = BC Therefore AB = BC = CD= DA. In ADB and BCA AD = BC [ Proved above] BD = AC [Given] AB = AB [ Common] Therfore DAB CBA [SSS Criteria of Congruence] --------(1) [ CPCT] As ABCD is a parallelogram, AD || BC Now AD || BC and AB is the transversal [ Co interior angles are supplementary ] [ Replacing B from equation 1] Now ABCD is a IIgm in which all sides are equal and one angle is .Thus ABCD is a square |
Illustration: If the side of a square ABCD whose diagonals intersect at O is 6cm find the length of OA and OB;
Solution: As the diagonals of a square are equal and bisect each other perpendicularly We can say that OA = OB = x(say) ..............(1) and AOB = AB = 6cm ...................(2) [Given] Now AOB is aright angled at O [By Pythagorous Theorem] Substituting the values from Eq (1) and (2), we get cm Hence OA = OB = cm |
In a square the diagonals are _________ and _________ to each other. | |||
Right Option : C | |||
View Explanation |
If the side of a square ABCD whose diagonals intersect at O is 10 cm find the length of OA and OB. | |||
Right Option : B | |||
View Explanation |
If the side of a square ABCD whose diagonals intersect at O is cm find the length of OA and OB. | |||
Right Option : A | |||
View Explanation |
About Abhyas metholodology the teachers are very nice and hardworking toward students.The Centre Head Mrs Anu Sethi is also a brilliant teacher.Abhyas has taught me how to overcome problems and has always taken my doubts and suppoeted me.
Abhyas is a complete education Institute. Here extreme care is taken by teacher with the help of regular exam. Extra classes also conducted by the institute, if the student is weak.
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My experience was very good with Abhyas academy. I am studying here from 6th class and I am satisfied by its results in my life. I improved a lot here ahead of school syllabus.
One of the best institutes to develope a child interest in studies.Provides SST and English knowledge also unlike other institutes. Teachers are co operative and friendly online tests andPPT develope practical knowledge also.
It was a good experience with Abhyas Academy. I even faced problems in starting but slowly and steadily overcomed. Especially reasoning classes helped me a lot.
I have spent a wonderful time in Abhyas academy. It has made my reasoning more apt, English more stronger and Maths an interesting subject for me. It has given me a habbit of self studying
My experience with Abhyas is very good. I have learnt many things here like vedic maths and reasoning also. Teachers here first take our doubts and then there are assignments to verify our weak points.
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It was good as the experience because as we had come here we had been improved in a such envirnment created here.Extra is taught which is beneficial for future.