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If in a !ABC,angleA=pi//3 and AD is a me...

If in a `!ABC,angleA=pi//3` and AD is a median , then

A

`2AD^(2)=b^(2)+c^(2)+bc`

B

`4AD^(2)=b^(2)+c^(2)+bc`

C

`6AD^(2)=b^(2)+c^(2)+bc`

D

none of these

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The correct Answer is:
B
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OBJECTIVE RD SHARMA ENGLISH-PROPERTIES OF TRIANGLES AND CIRCLES CONNECTED WITH THEM-Exercise
  1. If the sides of the triangle are the roots of the equation x^(3)-2x^(...

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  2. If AD, BE and CF are the medians of a Delta ABC, then evaluate (AD^(2)...

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  3. If a DeltaABC is right angled at B, then the diameter of the incircle ...

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  4. If a^(2),b^(2),c^(2) are in A.P.,then which of the following is also i...

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  5. If in a Delta ABC, sin ^(3) A + sin ^(3) B+ sin ^(3) C =3 sin A .Sin...

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  6. If the ex-radii of a triangle are in H.P.,then the corresponding sides...

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  7. If I is the incentre of a !ABC , then IA:IB:IC is equal to

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  8. In a triangle ABC ,the HM of the ex-radii is equal to

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  9. In a DeltaABC if r(1):r(2):r(3)=2:4:6, then a:b:c =

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  10. If in a !ABC,angleA=pi//3 and AD is a median , then

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  11. In a triangle ABC cos^(2)A/2+cos^(2)B/2+cos^(2)C/2=

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  12. The base of a triangle is 80cm and one of the base angles is 60^(@).If...

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  13. In a DeltaABC if r(1)=16,r(2)=48 and r(3)=24, then its in-radius ,is

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  14. In a △ ABC if a =26, b= 30 and cos C =63/65, then r(2) =

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  15. In a triangle ABC if sides a = 13, b =14 and c = 15, then reciprocals...

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  16. In a A B C , ifsinAa n dsinB are the roots of the equation c^2x^2-c(a...

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  17. If a , b , c denote the sides of a !ABC such that the equation x^(2)+...

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  18. In a Delta ABC if b+c=2a and /A=60^@ then Delta ABC is

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  19. In a Delta ABC, if b=20, c=21and sin A =3/5, then the value of a is

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  20. Let A, B and C are the angles of a plain triangle and tan(A/2)=1/3...

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