Question:

One more trigonometry question?

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cot A+ cosec A-1

------------------------ = cosec A + cot A

cot A-cosec A +1

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3 ANSWERS


  1. LHS, Numerator:

    cot A+ cosec A -1 =  cotA + cosecA - (cosec²A - cot²A)

    [since sin²A + cos²A = 1 => 1- cos²A = sin²A

    =>Divide by sin²A both sides, cosec²A - cot²A = 1]

      = cotA + cosecA - (cosecA + cotA)(cosecA - cotA)

      = (cosecA + cotA) (cotA - cosecA + 1) [taking the common factor cosecA + cotA]

    Hence LHS:

    (cosecA + cotA) (cotA - cosecA + 1) / (cotA - cosecA + 1)

    = cosecA + cotA = RHS

    AJM


  2. now if i start like this....

    cotA+cosecA-1 = cotA +cosecA-(cosecA^2-CotA^2)

                            = (cotA + cosecA)-(cosecA-cotA)(cosecA+cotA)

                            = (cosecA+cotA) [1-(cosecA-cotA)]

                            = (cosecA+cotA)(1-cosecA + cotA)

    so it's

    cot A+ cosec A-1

    ------------------------ = cosec A + cot A

    cot A-cosec A +1

  3. cot A+ cosec A-1

    = cot A + cosec A - (cosec^2 A - cot^2 A)

    = cot A + cosec A - (cosec A + cot A)(cosec A - cot A)

    = (cot A + cosec A) ( 1- cosec A + 1)

    hence

    (cot A+ cosec A-1)/( 1- cosec A + 1) = cot A + cosec A

      

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