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If a:b: c = 3: 5: 7 then cos A : cos B ...

If a:b: c = 3: 5: 7 then cos A : cos B : cos C

A

` 13: 11: -7`

B

` 14: 11 : 7`

C

` 14: 11 : 8 `

D

` 13: 11: 7`

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The correct Answer is:
A
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AAKASH SERIES-PROPERTIES OF TRIANGLES-PRACTICE EXERCISE
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  2. If sides of a triangles are in the ratio x: y : sqrt( x^(2) +xy + y...

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  3. If a:b: c = 3: 5: 7 then cos A : cos B : cos C

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  4. If A = 60 ^(@) " then " ( 1)/(a+b) + (1) /( a+ c) =

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  5. In Delta ABC if a =2, b= 3, c = 4 then cos A + cos B + cos C =

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  6. In Delta ABC , 2ac sin ""( 1)/(2) (A-B+C)=

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  7. The sides of a triangles are x^(2) +3x + 3, 2x+ 3 and x^(2) + 2x th...

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  8. In Delta ABC , if c^(4) - 2 (a^(2) + b^(2) ) c^(2) + a^(4) +a^(2)...

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  9. In triangle ABC , a = 4, b = 3 and angle A = 60^(@) . Then c is root...

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  10. The roots of x^(2) - 2 sqrt 3 x+ 2=0 represent two sides of a tria...

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  11. (c- b cos A )/( b - c cos A ) =

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  12. ( b+c) cos A + ( c+a) cos B +( a+b) cos C =

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  13. In Delta ABC , if a( b cos C + c cos B ) = 2ka^(2) , then k=

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  14. In Delta ABC , if A,B , C are in A.P. The (a+c)/( sqrt(a^(2) -ac + ...

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  15. InDelta ABC , a( b cos C - c cos B) =

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  16. In Delta ABC , (sin A(a- b cos C))/( sin C ( c-b cos A)) =

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  17. If a,b,c are in A.P. Then cos "" ( A-C)/( 2) cosec ""(B)/(2) =

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  18. In Delta ABC , b = sqrt 3+ 1 , c sqrt3-1 and angle A = 60 ^(@) the...

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  19. If C = A - B = 60 ^(@) " then " (a-b)/ (c )=

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  20. In Delta ABC , if tan ""( A)/(2) = t cot ""(( B- C)/( 2)) , " the...

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