If 1 ° = α radians then the approximate value of cos 60 ° 1 ' is

If 1°=α radians then the approximate value of cos60°1' is
  1. 1 2 + α 3 1 2 0
  2. 1 2 - α 1 2 0
  3. $\frac{1}{2} - \frac{\alpha\sqrt{3}}{120}$
  4. None of these

Solution

Let  y=cosx⇒dydx=−sinx

As we know fa+h≅fa+hf'a,

where h is very small

Now, 60°1'≅π3+α60   ∵1°=60' 

So, cosπ3+α60≅cosπ3-α60sinπ3

cosπ3+α60≅12-α6032

Asked in: MHT CET Full Test 4

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