Question

A right △ABC is inscribed in circle k(O, r). Find the radius of this circle if:

Answer 1

We have been given that a right △ABC is inscribed in circle k(O, r).

m∠C = 90°, AC = 18 cm, m∠B = 30°. We are asked to find the radius of the circle.

First of all, we will draw a diagram that represent the given scenario.

We can see from the attached file that AB is diameter of circle O and it a hypotenuse of triangle ABC.

We will use sine to find side AB.

$\text{sin}=\frac{\text{Opposite}}{\text{Hypotenuse}}$

$\text{sin}(30^{\circ})=\frac{AC}{AB}$

$\text{sin}(30^{\circ})=\frac{18}{AB}$

$AB=\frac{18}{\text{sin}(30^{\circ})}$

$AB=\frac{18}{0.5}$

$AB=36$

Wee know that radius is half the diameter, so radius of given circle would be half of the 36 that is $\frac{36}{2}=18$.

Therefore, the radius of given circle would be 18 cm.