Angles in Triangles and Quadrilaterals

This video introduces two circle theorems: the triangle in a semicircle and the tangent-radius theorem. It explains that a triangle in a semicircle always has a 90° angle at the circumference, and a tangent and radius always form a 90° angle. The video provides examples of applying these theorems to solve for unknown angles in triangles and quadrilaterals, using both basic arithmetic and algebraic methods.

What is the angle formed by a triangle in a semicircle?

• 120°

• 90°

• 60°

• 45°

What is the angle between a tangent and a radius?

• 90°

• 120°

• 60°

• 45°

In a triangle, what is the sum of all internal angles?

• 270°

• 90°

• 360°

• 180°

If one angle in a triangle is 90° and another is 20°, what is the third angle?

• 90°

• 70°

• 60°

• 80°

Which rule is used to determine the angles in a triangle?

• Sum of angles in a triangle

• Pythagorean theorem

• Circle theorem

• Tangent-radius theorem

What is the sum of angles in a triangle?

• 360°

• 270°

• 180°

• 90°

What is the missing angle if a triangle has angles of 90° and 20°?

• 80°

• 90°

• 70°

• 60°

What is the sum of angles in a triangle?

• 360°

• 90°

• 180°

• 270°

What is the missing angle if a triangle has angles of 90° and 20°?

• 90°

• 80°

• 70°

• 60°

What is the missing angle if a triangle has angles of 90° and 30°?

• 50°

• 80°

• 60°

• 70°