A is the centre of the circle. AB and AC are the radii. F is an exterior point. FB and FC are tangents. Therefore B and C are the respective points of contact. You may Drag A (the cente), B , C (the point of contacts) to experience the following : 1) According to the radius tangent theorem , radii (AB and AC) are perpendicular to the tangents (FB and FC respectively). 2) According to the two tangent theorem, the two tangents from the exterior point F, FB is equal to FC. 3) The opposite angles of the quadrilateral (formed by the two tangents and two radii) are supplementary, means they add to give 180 degrees . 4) Can you guess what type of quadrilateral will ABFC be then ?
