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In Delta ABC if 5r = 2R then cos A ...

In ` Delta ABC ` if 5r = 2R then cos A + cos B + cos C =

A

` ( 7)/(5) `

B

` (3)/(4)`

C

` ( 2)/(5) `

D

` ( 4)/( 7) `

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The correct Answer is:
A
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AAKASH SERIES-PROPERTIES OF TRIANGLES-PRACTICE EXERCISE
  1. The inventre of Delta ABC is the of its excentral triangle

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  2. cos ^(2) ((A)/(2)) + cos ^(2) ((B)/(2)) +cos ^(2) (( C )/(2)) =

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  3. In Delta ABC if 5r = 2R then cos A + cos B + cos C =

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  4. If p1 ,p2,p3 are the lengths of altitudes of Delta ABC from the ...

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  5. If P1 , P2 , P3 are lengths of altitudes of a triangle from its v...

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  6. In Delta ABC, if a= 30 ,b= 24, c= 18 , then r=

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  7. In Delta ABC, if a= 13, b= 14, c= 15 , then r2 =

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  8. If 2,3,6 are exradii of triangle , then its inradius is

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  9. If the area of a triangle is 6.sq units and its inradius is 2 unit...

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  10. If the area of Delta ABC with sides a,b,c is Delta, then the are...

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  11. In Delta ABC, if r2 = 3 , r3 = 4 then the length of the altitude ...

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  12. If r1 = 36,r2 = 18 r3 = 12 then the area of Delta ABC is

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  13. If angle C = 90 ^(@) ," then " 2(r + R) =

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  14. If r1 = r2 = r3 then triangle is

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  15. if x,y,z are the distances of the vertices of Delta ABC from its...

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  16. If the side of an equilateral triangle is 2sqrt3 then each of exrad...

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  17. In an equilateral triangle ABC, P1 is length of altitude from A ...

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  18. a( r r 1 +r2r3) =

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  19. ( r1+ r2) (r2+r3) (r3+r1) =

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  20. If I1 is the centre of the first escribed circle , then the value ...

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