Regina draws a triangle inside a circle; she labels the vertices ABC , with the diameter as AB and the inscribed angle as C . She draws the length of AB 14 cm long, and AC 8 cm long. Using what you know about inscribed angles, what will be the approximate angle measure of B ?(1 point)

Responses

70°
70°

55°
55°

90°
90°

35°
35°

1 answer

In a triangle inscribed in a circle where one side is the diameter, the angle opposite to that side (the inscribed angle) is a right angle (90°). This is a consequence of Thales' theorem.

In this case, since AB is the diameter of the circle, angle C must be 90°.

To find angle B, we can use the properties of triangle ABC. Since angle C is 90°, angles A and B must sum up to 90° as well:

\[ \angle A + \angle B = 90° \]

To find the values of angles A and B, we can use the given lengths of sides AC and AB. We can apply the sine rule or some trigonometric ratios, but with the provided information:

Since side AB (14 cm) is opposite to angle C (90°) and AC (8 cm) is opposite to angle B, we can use the sine function:

\[ \sin(B) = \frac{AC}{AB} = \frac{8}{14} = \frac{4}{7} \]

Using the inverse sine function to find angle B:

\[ B ≈ \arcsin\left(\frac{4}{7}\right) \]

Calculating this gives us approximately:

\[ B ≈ 0.515 \text{ radians} ≈ 29.74° \]

However, since the inscribed angles need to sum to 90° and angle A will complement B:

\[ \angle A + \angle B = 90° \]

If angle C = 90°, we typically can't directly calculate angle B without angle A's information. However, it is clear from the options provided that the one fitting structurally due to the circle's properties is:

B must be less than 90° and one of those within the circle property.

In finality without loss of information that may indicate precision: The response that fits closely:

We've found B approximately 35° (due to maintaining triangles), thus the right answer is:

35°.