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    ​If A lies in the second quadrant and 13sin⁡A−12=0, then 5sin⁡A+12cos⁡A+tan⁡2A−(sec⁡2A−1)=?\text{If
    Question

    If A lies in the second quadrant and 13sinA12=0, then 5sinA+12cosA+tan2A(sec2A1)=?\text{If } A \text{ lies in the second quadrant and } 13\sin A - 12 = 0, \text{ then } 5\sin A + 12\cos A + \tan^2 A - (\sec^2 A - 1) = ?​​

    A.

    0

    B.

    485\frac{48}{5}​​

    C.

    245\frac{24}{5}

    D.

    245-\frac{24}{5}

    Correct option is A

    Given:

    13sinA12=013\sin A - 12 = 0 

    5sinA+12cosA+tan2A(sec2A1)=?5\sin A + 12\cos A + \tan^2 A - (\sec^2 A - 1)= ? 

    Concept Used:

    sin2A+cos2A=1\sin^2 A + \cos^2 A = 1 

    tanA=sinAcosA\tan A = \frac{\sin A}{\cos A} 

    sec2A1=tan2A\sec^2A-1= \tan^2A 

    Solution: 

    13sinA12=013\sin A - 12 = 0 

    =>13sinA=12\Rightarrow 13\sin A = 12 

    =>sinA=1213\Rightarrow \sin A = \frac{12}{13} 

    Using the Pythagorean identity , sin2A+cos2A=1,\text{Using the Pythagorean identity }, \\ \ \\ \sin^2 A + \cos^2 A = 1, 

    (1213)2+cos2A=1 =>144169+cos2A=1 =>cos2A=25169\left(\frac{12}{13}\right)^2 + \cos^2 A = 1 \\ \ \\ \Rightarrow \frac{144}{169} + \cos^2 A = 1 \\ \ \\ \Rightarrow \cos^2 A = \frac{25}{169} 

    Since A lies in the second quadrant,(cosA=513)\text{Since A lies in the second quadrant}, ( cos A = -\frac{5}{13}) 

    5sinA+12cosA+tan2A(sec2A1)5\sin A + 12\cos A + \tan^2 A - (\sec^2 A - 1) 

    5sinA+12cosA+tan2Atan2A5\sin A + 12\cos A + \tan^2 A - \tan^2 A 

    5sinA+12cosA5\sin A + 12\cos A  

    Now, substitute the values of sinA  and  cosA from above 

    5×1213+12×(513)5 \times \frac{12}{13} + 12 \times \left(-\frac{5}{13}\right) 

    60136013=0\frac{60}{13} - \frac{60}{13} = 0 

    ​Thus, the value of the expression is 0.


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