The radius of circle O is 18, and OC = 13. Find AB. Round to the nearest tenth, if necessary. (The figure is not drawn to scale.)    A. 12.4 B. 3.8 C. 24.9 D. 44.4

The radius of circle O is 18 and OC 13 Find AB Round to the nearest tenth if necessary The figure is not drawn to scale A 124 B 38 C 249 D 444 class=

Respuesta :

We are asked to solve for the length AB of the given circle with center O.
The angle of OCB is 90°, therefore, we can apply SOH CAH TOA and Pythagorean theorem in the problem.

OB² = OC² + CB² where OB is the radius which means its length is equal to 18 units. 
OB = 18 units
OC = 13 units

18² = 13² + CB²
CB = 12.45 units

AB is twice of CB length, therefore we have:
AB = 12.45 * 2
AB = 24.9 units

The answer is the letter "C".

Radius of circle is straight line segment connecting the center of circle to its circumference. The length of AB for given context is: |AB| = 24.9 units.

The Pythagoras theorem:

If ABC is a triangle with AC as the hypotenuse and angle B with 90 degrees then we have:

[tex]|AC|^2 = |AB|^2 + |BC|^2[/tex]

where |PQ| means length of line segment PQ

What is the relation between line perpendicular to chord from the center of circle?

If the considered circle has center O and chord AB, then if there is perpendicular from O to AB at point C, then that point C is bisecting(dividing in two equal parts) the line segment AB.

Or

|AC| = |CB|

For given case, we're given that:

  • Length of radius of circle = 18 units = |OB| (as OB is a radius)
  • Length of OC = |OC| = 13 units
  • To find: Length of AB = |AB| = |AC| + |CB| = 2|CB| (by aforesaid relation, as C will bisect the line segment AB)

Since we've got OCB as right angled triangle(a triangle with one of the angle as of right angled (90 degrees) ), thus, using Pythagoras theorem, we get:

[tex](|OB|)^2 = (|OC|)^2 + (|CB|)^2 \\18^2 = 13^2 + (|CB|)^2\\\\|CB| = \sqrt{18^2 - 13^2} \text{ \: Positive root as length is non-negative quantity}\\\\|CB| = \sqrt{155} \approx 12.45 \: \rm units[/tex]

Thus, we get:

|AB| = 2|CB| ≈ 24.9 units

Thus, The length of AB for given context is: |AB| = 24.9 units.

Learn more about Pythagoras theorem here:

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