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    If cosec α = √2, evaluate (2sin2⁡α+3cos2⁡α)(cosec2α+cot2α)\frac{(2 sin²⁡α+3 cos²⁡α)}{(cosec^2 α+cot^2 α)}(cosec2α+cot2α)(2sin2⁡α+3cos2⁡α)​​​
    Question

    If cosec α = √2, evaluate (2sin2α+3cos2α)(cosec2α+cot2α)\frac{(2 sin²⁡α+3 cos²⁡α)}{(cosec^2 α+cot^2 α)}​​

    A.

    5/6

    B.

    5/12

    C.

    5/3

    D.

    5/2

    Correct option is A

    Given:

    cosecα=2cosec \alpha = \sqrt{2}​​

    Formula used:

    cosecα=1sinα cosec \alpha = \frac{1}{sin \alpha}

    sinα=1/2\sin \alpha = 1/\sqrt{2}​​

    sin2α+cos2α=1\sin^2 \alpha + \cos^2 \alpha = 1​​

    cosα=1sin2α\cos \alpha = \sqrt{1 - \sin^2 \alpha}​​

    Solution:

    sinα=12,sosin2α=12\sin \alpha = \frac{1}{\sqrt{2}} , so \sin^2 \alpha =\frac{ 1}{2}​​

    cos2α=112=12\cos^2 \alpha = 1 -\frac{ 1}{2}= \frac{1}{2}​​

    2sin2α+3cosαcosec2α+cot2α\frac{2\sin^2 \alpha + 3\cos \alpha}{\cosec^2 \alpha + \cot^2 \alpha}​​

    First, calculate the numerator:

    Numerator = 2sin2α+3cos2α2\sin^2 \alpha + 3\cos^2 \alpha​​

    Numerator = 2×12+3×122\times\frac{1}{2} + 3\times\frac{1}{{2}}​​

    Numerator = 1+32=2.51 + \frac{3}{{2}} = 2.5​​

    Now, calculate the denominator:

    Denominator = cosec2α+cot2α\cosec^2 \alpha + \cot^2 \alpha​​

    We know cosecα=2cosec \alpha = \sqrt{2}​​

    cosec2α=(2)2=2\cosec^2 \alpha = (\sqrt{2})^2 = 2​​

    cotα=cosαsinα=1212=1\cot \alpha = \frac{cos \alpha }{\sin \alpha} =\frac{\frac{ 1}{\sqrt{2}}} { \frac{1}{\sqrt{2}}}= 1​​

    cot2α=1\cot^2 \alpha = 1​​

    Denominator = 2 + 1 = 3

    Finally, the expression becomes:

    Result=2.53=56\text{Result} = \frac{2.5}{3} = \frac{5}{6}​​

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