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Prove that b^2 + c^2 -a^2 = bc, then A...

Prove that
`b^2 + c^2 -a^2 = bc`, then A = `60^@`

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`b^2 + c^2 -a^2 = bc`
or, `(b^2 + c^2 -a^2)/(abc) = 1/2` or cosA = 1/2 or A = `60^@`
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MBD PUBLICATION-TRIGONOMETRIC FUNCTIONS-QUESTION BANK
  1. Prove that If (b+c)/5 = (c+a)/6 = (a+b)/7 then sinA : sinB : sinC ...

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  2. Prove that If A : B: C = 1: 2: 3 then sinA : sinB : sinC = 1:sqrt3...

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  3. Prove that b^2 + c^2 -a^2 = bc, then A = 60^@

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  4. Prove that If A: B: C = 1: 2: 7, then c:a =(sqrt5+1) : (sqrt5-1)

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  5. If cosA = 12/13 , cosB = 5/13, then find a:b.

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  6. If a = 7 , b= 3, c=5 then find A.

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  7. If a = 8,b=6 , C= 4 find tan B/2.

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  8. If a/(secA) = b/(secB) and a ne b then find C.

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  9. If a = 48, b= 35 ,angleC = 60^@ then find c.

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  10. In Delta ABC prove that a sin(B-C) + bsin(C-A) + c sin(A-B) = 0

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  11. In Delta ABC prove that a sin(B-C) + bsin(C-A) + c sin(A-B) = 0

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  12. In Delta ABC prove that sin(B-C)//sin(B+C) = (bcosC - c cosB)//(bcos...

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  13. In Delta ABC prove that sum a^2sin(B-C)//sin(B+C) = 0

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  14. In Delta ABC prove that a^2(cos^2B - cos^2C) + b^2(cos^2C - cos^2A) ...

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  15. In Delta ABC prove that (b^2-c^2)/(a^2) sin2A + (c^2-a^2)/(b^2) sin2...

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  16. In Delta ABC prove that a^2(b^2 + c^2 - a^2)/(sin2A) = b^2(c^2 + a^2...

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  17. In Delta ABC prove that sum (cosA)/(sinBsinC)= 2

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  18. In Delta ABC prove that (a^2 -b^2 + c^2) tanB = (a^2 + b^2 - c^2) ta...

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  19. In Delta ABC prove that (b^2-c^2)cotA + (c^2-a^2)cotB + (a^2-b^2)cot...

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  20. In Delta ABC prove that (b+c)/a = (cosB + cosC)/(1-cosA)

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