Question

define normal line

Answer 1

the line perpendicular to the slope (or tangent) of the curve(or original line) at a specified point

Answer 2

are there probs of this in cal

Answer 3

Finding perpendicular lines is pretty common in calculus, yes.
It mostly just practice using derivatives to find slope, then recalling what you know about perpendicular slopes from algebra.
When you get to 3D vectors, you'll learn other techniques.

Answer 4

thank you!