Question
Points A, B and C are all on the
circumference of the circle. O represents the centre. DA and DB are tangents to the circle. Angle BDO = 31°
Work out the size of angle x
Answer:
62°
Explanation:
To solve for the above question, we would be using circle theorems.
Step 1
Angle OBD = 90° This is because a radius and a tangent meet at 90°
Step 2
The sum of Angles in a triangle = 180°
180° = Angle OBD + Angle BDO + Angle BOD
180° = 90° + 31° + Angle BOD
Angle BOD = 180° - (90° + 31°)
= 180° - 121°
Angle BOD = 59°
Step 3
Angle BOD = Angle AOD because they are congruent ,therefore, Angle AOD = 59°
Step 4
The sum of angles of a straight line = 180°
Angle BOD, Angle AOD and Angle x are angles on a straight line
Hence,
180° = Angle BOD + Angle AOD + Angle x
180° = 59° + 59° + x
x = 180° - ( 59 + 59)°
x = 180° - 118°
x = 62°
Therefore Angle x = 62°