Answer:
105°
Step-by-step explanation:
The measure of an inscribed angle is half the measure of the arc it subtends. For an arc of 210°, an inscribed angle that subtends it will have a measure of 105°.
We normally think of the sides of an inscribed angle as being a chord. However, that chord can be considered part of a secant. When the two points of intersection with the circle get arbitrarily close together, the chord becomes a point, and the secant becomes a tangent.
That is, the angle made by this geometry is simply a degenerate case of an inscribed angle. The relationship with the arc measure is unchanged.
m∠1 = 105°
