Find the value of c if the line y = 3x + c is a tangent to the circle x2+y2=10
-10
If L is a tangent OP, the perpendicular distance of centre O from L will be equal to radius.
⇒OP=∣∣∣c√12+32∣∣∣=∣∣∣c√10∣∣∣
We have OP=r=√10
⇒∣∣∣c√10∣∣∣=√10
⇒c√10=±√10
⇒c=±10