Important: When a tangent and a secant, two secants, or two tangents intersect outside a circle then the measure of the angle formed is one-half the positive difference of the measures of the intercepted arcs.
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∠SOT = xº ∠ROB = (4x)º ∠RTB = 28º
∠RTB = 1/2 (∠ROB - ∠SOT)
28º = 1/2 (4x - x) x = 18.6666666
Arc RS = 180 - 5x = 86.6666666º