Well not all lines are lines of symmerty, because if you draw a let's say a rectangle on a piece of paper and draw a diagonal line through it, well the two sides don't really lie perfectly on one another!!
Answer:
see explanation
Step-by-step explanation:
(a)
OC = OB ( both radii of the circle )
Thus Δ BOC is isosceles with congruent base angles.
∠ BOC = ∠ BCO = 50°
(b)
∠ ACB = 90° ( angle in a semicircle ), then
∠ ACO = 90° - 50° = 40°
OA = OC ( both radii of the circle )
Thus Δ ACO is isosceles with congruent base angles.
∠ BAC = ∠ ACO = 40°

well, we know the common difference is -3, to go from the 4th term to the 8th term, we need to add "d" 4 times or namely 3+4(-3), likewise to go from the 13th term to the 19th term we have to add "d" 6 times, or namely -24 + 6(-3).
