Question

Whether ab is tangent to circle c at point b

Answer 1

No

Explanation:

If segment AB is tangent to the circle, then angle CBA will be a right angle, making triangle ABC a right triangle. If triangle ABC is a right triangle, it's sides will fit the Pythagorean theorem...

(leg)^2 + (leg)^2 = (hypotenuse)^2

Does 8^2 + 16^2 = 19^2 ?

64 + 256 does not equal 361!

Triangle ABC is NOT a right triangle, so segment AB is not tangent to the circle.