Question

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°

35°
35°

55°
55°

70°

1 answer

Since triangle ABC is inscribed in a circle with AB as the diameter, angle C is a right angle according to the inscribed angle theorem. This means that angle B is not directly calculated but can be found using the sides of the triangle.

Given:

  • AB = 14 cm
  • AC = 8 cm

Using the Pythagorean theorem, we can find the length of side BC. Let the length of BC be represented as \( c \).

According to the Pythagorean theorem:

\[ AC^2 + BC^2 = AB^2 \]

Substituting the values we have:

\[ 8^2 + c^2 = 14^2 \]

This simplifies to:

\[ 64 + c^2 = 196 \]

Subtracting 64 from both sides gives:

\[ c^2 = 196 - 64 \] \[ c^2 = 132 \] \[ c = \sqrt{132} \approx 11.49 \text{ cm} \]

Now, we can use the sine rule or tangent to find angle B.

Using the sine function:

\[ \sin(B) = \frac{AC}{AB} \]

Substituting the known lengths:

\[ \sin(B) = \frac{8}{14} = \frac{4}{7} \approx 0.5714 \]

Now, we calculate angle B:

\[ B \approx \arcsin(0.5714) \approx 35° \]

Thus, the approximate angle measure of B is 35°.