From the image will be a 1 = 90 (tangent circle is perpendicular to the radius shall touch point) OA = OB, because it is the radius of a circle is the same as isosceles triangle AOB
the figure will be at an angle 1 = 90 (the line touch circle shall be perpendicular to a RADIUS at the point touch) OA=OB because because it is a RADIUS of the circle will be AOB same as an isosceles triangle