Geometry 15 – Questions on theorem 19 (circle questions)

You’ll learn

• Identify which arc an angle stands on, then pick the right circle theorem to apply
• Use Theorem 19 and its corollaries: semicircle angle = 90°, cyclic quad angles sum to 180°
• Spot isosceles triangles from equal radii and free 90° angles from tangent ⊥ radius
• Set up and solve an equation when circle angles are given algebraically (find x)