Answer:
m∠C = 102°
Step-by-step explanation:
This is a quadrilateral inscribed in a circle
The sum of opposite angles in a cyclic quadrilateral is equal to 180°
m∠D + m∠B = 180°
m∠B = 180° - m∠D
m∠B = 180° - 80°
m∠B = 100°
We know what m∠B
We have external angles outside the circle.
m∠CDA is opposite m∠B
m∠CDA = 2 × m∠B
m∠CDA = 2 × 100°
m∠CDA = 200°
m∠CDA is the sum of m∠CD and m∠DA
m∠CDA = m∠CD + m∠DA
m∠DA = m∠CDA - m∠CD
m∠DA = 200° - 116°
m∠DA = 84°
m∠DAB is an exterior angle also, hence,
m∠DAB is the sum of m∠DA and m∠AB
m∠DAB = m∠DA + m∠AB
m∠DAB = 84° + 120°
m∠DAB = 204°
Finally we can solve for m∠C
m∠DAB is Opposite m∠C
So, m∠C = 1/2 × m∠DAB
m∠C = 1/2 × 204
m∠C = 102°
