A projectile is projected with velocity of $25\, m / s$ at an angle $\theta$ with the horizontal. After t seconds its inclination with horizontal becomes zero. If $R$ represents horizontal range of the projectile, the value of $\theta$ will be : [use $g =10 m / s ^{2}$ ]

  • [JEE MAIN 2022]
  • A

    $\frac{1}{2} \sin ^{-1}\left(\frac{5 t^{2}}{4 R}\right)$

  • B

    $\frac{1}{2} \sin ^{-1}\left(\frac{4 R }{5 t ^{2}}\right)$

  • C

    $\tan ^{-1}\left(\frac{4 t ^{2}}{5 R }\right)$

  • D

    $\cot ^{-1}\left(\frac{ R }{20 t ^{2}}\right)$

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