The rate of change of the area of a circular disc with respect to its circumference when radius is 3 is:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) - 3 unit
circumference $C = 2πr$
area $a = πr^2$
$\frac{da}{dr}=2πr$
$\frac{dc}{dr}=2π⇒\frac{da}{dc}=r$
$\left.\frac{da}{dc}\right]_{r=3}=3$ unit