Answer:
A detailed diagram of he question has been attached with the explanation.
The value of angle A is 105 degree.
Step-by-step explanation:
The requisite knowledge is circle geometry especially the applications of the theorems that states that the angle at center is twice that at the remaining circumference. Also, the theorem of the sum of angles in a triangle which is 180 degree is also applied.
A step by step explanation is attached below.
