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

90°
90°

55°
55°

35°
35°

70°
70°

1 answer

To find the angle \( B \) in triangle \( ABC \), we note that since \( AB \) is the diameter of the circle, angle \( C \) is a right angle (90°), according to the inscribed angle theorem.

Given:

  • \( AB = 14 , \text{cm} \)
  • \( AC = 8 , \text{cm} \)

Using the Pythagorean theorem for right triangle \( ABC \): \[ AB^2 = AC^2 + BC^2 \] Substituting the known values: \[ 14^2 = 8^2 + BC^2 \] \[ 196 = 64 + BC^2 \] \[ BC^2 = 196 - 64 \] \[ BC^2 = 132 \] \[ BC = \sqrt{132} \approx 11.49 , \text{cm} \]

Now, we can use the definition of the sine function to find angle \( B \): \[ \sin B = \frac{AC}{AB} \] Substituting the known lengths: \[ \sin B = \frac{8}{14} = \frac{4}{7} \]

Now we calculate \( B \): \[ B \approx \arcsin\left(\frac{4}{7}\right) \]

Using a calculator, we find: \[ B \approx 46.57^\circ \]

However, we need to find angle \( A \) using the angle sum property of triangles: \[ A + B + C = 180^\circ \] Substituting \( C = 90^\circ \): \[ A + B + 90^\circ = 180^\circ \] \[ A + B = 90^\circ \] Thus, \[ A = 90^\circ - B \approx 90^\circ - 46.57^\circ \approx 43.43^\circ \] Finally, we can find angle \( B \) still: Knowing \( A + B = 90^\circ \), thus angle \( B \) remains around 46.57°, close to selected choices provided.

The response closest and most reasonable choice for an approximate angle measure for angle \( B \) could then be considered to align with what angles are available. However, since this approach aligns with approximate number rounding:

The options presented in the problem do not contain 46.57° but among the options arranged, response \( 55° \) seems to be the most plausible leaning direction when rounding, as approximate can skew higher.

Thus, Response: 55°