The angle in question is half the measure of the angle subtended by the chord, which is 60°. The chord is equal to a radius in length, so it and the radii to its ends form an equilateral triangle. The angle at the center of the circle is then 60°.
Half the measure of the subtended angle is 60°/2 = 30°.
Parallel lines are lines in a plane that are always the same distance apart. Parallel lines never intersect. Perpendicular lines are lines that intersect at a right (90 degrees) angle. Hope this helps :))
