Maths-
General
Easy

Question

f a comma blank b blankandblank A are given in a triangle and c subscript 1 end subscript comma blank c subscript 2 end subscript are the possible values of the third side, then c subscript 1 end subscript superscript 2 end superscript plus c subscript 2 end subscript superscript 2 end superscript minus 2 c subscript 1 end subscript c subscript 2 end subscript cos invisible function application A equals is equal to

  1. 4 a to the power of 2 end exponent sin invisible function application 2 A  
  2. 4 a to the power of 2 end exponent sin to the power of 2 end exponent invisible function application A  
  3. 4 a to the power of 2 end exponent cos invisible function application 2 A  
  4. 4 a to the power of 2 end exponent cos to the power of 2 end exponent invisible function application A  

The correct answer is: 4 a to the power of 2 end exponent cos to the power of 2 end exponent invisible function application A


    We haveblank cos invisible function application A equals fraction numerator b to the power of 2 end exponent plus c to the power of 2 end exponent minus a to the power of 2 end exponent over denominator 2 b c end fraction
    rightwards double arrow c to the power of 2 end exponent minus 2 blank b c cos invisible function application A plus b to the power of 2 end exponent minus a to the power of 2 end exponent equals 0 comma blankwhich is quadratic inblank ´ c ´
    therefore c subscript 1 end subscript plus c subscript 2 end subscript equals 2 b cos invisible function application A blankandblank c subscript 1 end subscript c subscript 2 end subscript equals b to the power of 2 end exponent minus a to the power of 2 end exponent (i)
    therefore c subscript 1 end subscript superscript 2 end superscript plus c subscript 2 end subscript superscript 2 end superscript minus 2 c subscript 1 end subscript c subscript 2 end subscript cos invisible function application 2 A
    equals open parentheses c subscript 1 end subscript plus c subscript 2 end subscript close parentheses to the power of 2 end exponent minus 2 c subscript 1 end subscript c subscript 2 end subscript minus 2 c subscript 1 end subscript c subscript 2 end subscript cos invisible function application 2 A [using Eq.(i)]
    equals open parentheses c subscript 1 end subscript plus c subscript 2 end subscript close parentheses to the power of 2 end exponent minus 2 c subscript 1 end subscript c subscript 2 end subscript open parentheses 1 plus cos invisible function application 2 A close parentheses
    equals 4 b to the power of 2 end exponent cos to the power of 2 end exponent invisible function application A minus 2 open parentheses b to the power of 2 end exponent minus a to the power of 2 end exponent close parentheses. blank 2 cos to the power of 2 end exponent invisible function application A equals 4 a to the power of 2 end exponent cos to the power of 2 end exponent invisible function application A

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