Answer:
OG = 8.7
Explanation:
The angle a tangent makes with a radius at the point of tangency is a right angle. That means ΔOGH is a right triangle.
The tangents to a circle from an external point are congruent, so GH = GI = 6.3. Now we know the sides of the right triangle are of lengths 6 and 6.3. The hypotenuse, OG is found using the Pythagorean theorem.
OG² = OH² +GH²
OG² = 6² +6.3² = 75.69
OG = √75.69 = 8.7
The length of OG is 8.7 units.
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Additional comment
You might recognize this triangle as a 0.3 multiple of the Pythagorean triple (20, 21, 29).