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(cos ^(2) ((B-C)/( 2)) )/( (b+c)^(2))+(...

` (cos ^(2) ((B-C)/( 2)) )/( (b+c)^(2))+( sin ^(2)((B-C)/( 2)) )/( (b-c)^(2))= `

A

` (1)/(a^(2))`

B

` ( 2)/( a^(2))`

C

` ( a^(2))/( 2) `

D

` a^(2) `

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The correct Answer is:
A
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AAKASH SERIES-PROPERTIES OF TRIANGLES-EXERCISE - II
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  2. In Delta ABC , a( b^(2) + c^(2) ) cos A +b ( c^(2) +a^(2)) cos B + c(...

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  3. (cos ^(2) ((B-C)/( 2)) )/( (b+c)^(2))+( sin ^(2)((B-C)/( 2)) )/( (b-c...

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  4. In DeltaABC,(b-c)/(b+c)cot""A/2+(b+c)/(b-c) tan""A/2=

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  5. If a=3,b =4,c= 5 ,then sin 2B is

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  6. If a cos ^(2) "" (C )/(2) +c cos ^(2) "" (A)/(2) = (3b)/( 2 ) " th...

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  7. In Delta ABC , if cos A + 2 cos B + cos C = 2 then a,b,c = in

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  8. If sin theta = a/(b+c) then show that cos theta = (2sqrt(bc))/(b+c) co...

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  9. If a= ( b-c) sec theta " then " tan theta =

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  10. tan ""(A)/(2) + tan ""(B)/(2) + tan""(C )/(2) =

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  11. ( cot ""(A)/(2) + cot ""(B)/(2)+ cot ""( C )/( 2))/( cot A + cot B + ...

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  12. In a triangle ABC, if cot""A/2 cot""B/2=c, cot""B/2 cot""C/2=a and cot...

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  13. If (a+ b+ c) (b+ c-a) = kbc then

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  14. In Delta ABC ,if 5 cos C + 6 cos B = 4 and 6 cos A + 4 cos C = 5 " th...

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  15. In a triangle ABC, (s-a)/11=(s-b)/12=(s-c)/13, then tan^2 (A//2)=

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  16. In Delta ABC, if sin^2""A/2, sin^2""B/2,sin^2""C/2 are in H.P, then a,...

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  17. In Delta ABC, if tan A, tan B, tan C are in H.P., then a^2,b^2,c^2 are...

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  18. If in Delta ABC the sides a,b,c are in A.P. Then

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  19. If the altitudes of a triangle are in arithmetic progression, then the...

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  20. In Delta ABC if b=20,c=21 and sin A=3//5, then a=

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