A boat is observed from a tower of height $450 m$ at an angle of depression $42^{\circ}$ . After some time, it is observed that the boat is $200 m$ from the foot of the observation tower. Calculate the new angle of depression.
[Hint:from tables, you will find that tan $42^{0}$ = 0.9004]

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Solution

$tan x = \frac{200}{450} \Rightarrow x = {tan}^{- 1} (\frac{4}{9})$

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