O is the centre of the circle and ABC and EDC are tangents to the circle. Find the size of angle BCD. You must give reasons in your answers.
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Answer:
mBCD = 28°
Step-by-step explanation:
The angle mBFD inscribes the arc mBD, so we have that:
mBFD = mBD/2
76 = mBD/2
mBD = 152°
The angle mBOD is a central angle related to the arc mBD, so we have that:
mBOD = mBD = 152°
In the quadrilateral BODC, the sum of internal angles needs to be equal to 360° (property of all convex quadrilaterals). The angles mCBO and mCDO are right angles, because EDC and ABC are tangents to the circle.
So, we have that:
mBOD + mCDO + mBCD + mCBO = 360
152 + 90 + mBCD + 90 = 360
mBCD = 360 - 90 - 90 - 152
mBCD = 28°