4) A circle with centre of O and diameter COB is given if Ab and CD are parasllel then show quad AC is equal to Quad BD.
Your question must be:
A circle with centre O and diameter COB is given. If AB and CD are parallel, then show that chord AC is equal to chord BD.
Given: CB is the diameter of circle with center O. AB and CD are parallel.
To prove: AC = BD
We know that angle in a semicircle is a right angle.
So, ∠CAB = ∠BDC = 90°
We also know that the perpendicular distances between two parallel lines are equal.
Since, AB and CD are parallel to each other, so AC = BD.