Applications Of Derivatives Question 227
Question: If the normal to the curve $ y=f(x) $ at the point $ (3,,4) $ makes an angle $ \frac{3\pi }{4} $ with the positive x-axis then $ f’(3) $ is equal to
[IIT Screening 2000; DCE 2001]
Options:
A) $ -1 $
B) $ -\frac{3}{4} $
C) $ \frac{4}{3} $
D) $ 1 $
Show Answer
Answer:
Correct Answer: D
Solution:
Slope of the normal = $ \frac{-1}{dy/dx} $
therefore $ \tan \frac{3\pi }{4}=\frac{-1}{{{( dy/dx )} _{(3,,4)}}} $
\ $ {{( \frac{dy}{dx} )} _{(3,,4)}}=1 $ , \ $ {f}’(3)=1. $
BETA
