AB is a diameter of the circle, so it divides circle into two semicircles.
Inscribed Angle Theorem:
The measure of an inscribed angle is half the measure of the intercepted arc.
An especially interesting result of the Inscribed Angle Theorem is that an angle inscribed in a semi-circle is a right angle. That's why m∠
AQB=m∠ASB=m∠ALB=m∠ATB=m∠ARB=90°.It is impossible to find measure of ∠
BWD, its measure depends on measure of a central angle ∠WDB.
