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Show that (cosA)/(a)+(cosB)/(b)+(cosC)/(...

Show that `(cosA)/(a)+(cosB)/(b)+(cosC)/(c)=(a^(2)+b^(2)+c^(2))/(2abc)`

A

a

B

bc

C

`a+b+c`

D

abc

Text Solution

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The correct Answer is:
D
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AAKASH SERIES-PROPERTIES OF TRIANGLES-PRACTICE SHEET (EXERCISE-I) (LEVEL-I) (Straight- Objective Type Questions)
  1. (a ) /( b^(2) - c^(2)) + ( c )/( b^(2) - a^(2)) = 0 then B =

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  2. If 7,4 sqrt(3), sqrt(13), are the sides of DeltaABC then least angle i...

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  3. In DeltaABC, c (a cosB-b cosA)=

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  4. If the angles of the DeltaABC are in A.P., then a^(2)+c^(2)-ac=

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  5. If a = 26, b = 30 , cos C = ( 63 )/( 65) then C=

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  6. Show that (cosA)/(a)+(cosB)/(b)+(cosC)/(c)=(a^(2)+b^(2)+c^(2))/(2abc)

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

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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. If the angles A,B,C of a triangle are in A.P and sides a,b,c are in G....

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  10. if 6,10,4 are the sides of a triangle then its obtus angle is

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  11. In Delta ABC , ( bc cos A + c a cos B + ab cos C) /( cot A + cot B ...

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  12. Which of the following statements is true I : If (a+b+c)(a+b-c)=ab t...

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

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  14. In a Delta ABC, a (cos^2 B+cos^2 C)+cos A(c cos C+b cos B)=

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  15. For any angle theta, show that a cos theta = b cos ( C + theta) +...

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  16. In DeltaBC, sum (b+c)cos=A

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  17. In triangle ABC//a(b^(2)+c^(2))cosA+b(c^(2)+a^(2))(cosB+c(a^(2)+b^(2))...

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  18. Which of the following statements is true I : In a DeltaABC if a= R...

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  19. In Delta ABC, if 3 tan ""A/2 tan""C/2=1 then a,b,c are in

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  20. In a DeltaABC, if "tan"(A)/(2),"tam"(B)/(2),"tan"(C)/(2) are in H.P th...

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