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

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

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If a = 7 , b= 3, c=5 then
cosA = `(b^2 + c^2 + a^2)/(2bc) = (9 + 25 - 49)/(2 xx 3 xx 5) = (-15)/(2xx3xx5) = -1/2`
`therefore` cosA = -1/2 or A = `120^@`
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MBD PUBLICATION-TRIGONOMETRIC FUNCTIONS-QUESTION BANK
  1. Prove that If A: B: C = 1: 2: 7, then c:a =(sqrt5+1) : (sqrt5-1)

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

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

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

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

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

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

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

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

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

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

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  18. In Delta ABC prove that sum a^3 sin(B-C)= 0

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  19. In Delta ABC prove that (b+c)cosA + (c+a)cosB + (a+b)cosC = a+b+c

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  20. In Delta ABC prove that 2(bc cosA + ca cosB + ab cosC) = a^2 + b^2 +...

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