✒️CIRCLES
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[tex] \large\underline{\mathbb{PROBLEMS}:} [/tex]
- 1. If AG = 24 cm, what is AC?
- 2. If OA = 5 cm and OG = 3 cm, what is CG?
- 3. If OG = 6 cm and AC = 16 cm, what is BG?
- 4. If BG = 2 cm and OC = 10 cm, what is AG?
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[tex] \large\underline{\mathbb{ANSWERS}:} [/tex]
[tex] \qquad \Large \: \rm{1) \: AC = 48cm} [/tex]
[tex] \qquad \Large \: \rm{2) \: CG = 4cm} [/tex]
[tex] \qquad \Large \: \rm{3) \: BG = 4cm} [/tex]
[tex] \qquad \Large \: \rm{4) \: AG = 6cm} [/tex]
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[tex] \large\underline{\mathbb{SOLUTIONS}:} [/tex]
First, we need to look in some of its features:
- Point O is the center of the circle. OC, OA, OB are radii, making them equidistant to each other.
- Drawing chord AC creating an isosceles ∆AOC.
- Radius OB is perpendicular to chord AC intersects at point G. Thus, it bisects AC which makes AG ≅ CG.
- Since OC ≅ OA, OG ≅ OG, AG ≅ CG, then we have created two congruent right triangles ∆CGO and ∆AGO
[tex] \: [/tex]
Solve for the measures:
#1: If AG = 24 cm, what is AC?
- AG is half of AC. Thus, twice of AG is equal to AC. We can say that twice of 24cm is 48cm. Therefore, AC is 48cm
[tex] \: [/tex]
#2: If OA = 5 cm and OG = 3 cm, what is CG?
» Focus on ∆AGO. Find AG using the Pythagorean Theorem.
- [tex] (OG)^2 + (AG)^2 = (OA)^2 [/tex]
- [tex] (3cm)^2 + (AG)^2 = (5cm)^2 [/tex]
- [tex] 9cm^2 + (AG)^2 = 25cm^2 [/tex]
- [tex] (AG)^2 = 25cm^2 - 9cm^2 [/tex]
- [tex] (AG)^2 = 16cm^2 [/tex]
- [tex] \sqrt{(AG)^2} = \sqrt{16cm^2} [/tex]
» Thus, AG measures 4cm. We can say that AG is congruent to CG. Therefore, CG is 4cm as well.
[tex] \: [/tex]
#3: If OG = 6 cm and AC = 16 cm, what is BG?
» Focus on any right triangles, like ∆AGO, because we will be finding for the radius. Solve for OA using the Pythagorean Theorem.
- [tex] (OG)^2 + (AG)^2 = (OA)^2 [/tex]
- [tex] (6cm)^2 + (AG)^2 = (OA)^2 [/tex]
» We know that AG is half of AC. Thus, half of 16cm is 8cm, which is AG.
- [tex] (6cm)^2 + (8cm)^2 = (OA)^2 [/tex]
- [tex] 36cm^2 + 64cm^2 = (OA)^2 [/tex]
- [tex] 100cm^2 = (OA)^2 [/tex]
- [tex] \sqrt{100cm^2} = \sqrt{(OA)^2} [/tex]
» OA measures 10cm. Thus, OB is 10cm as well since it is also a radius. Find BG that is the difference of OB and OG since the sum of the measures of BG and OG is OB.
- [tex] BG = OB - OG [/tex]
- [tex] BG = 10cm - 6cm [/tex]
[tex] \therefore [/tex] BG measures 4cm
[tex] \: [/tex]
#:. If BG = 2 cm and OC = 10 cm, what is AG?
» Focus on ∆AGO. OC is equidistant to OA. Thus, OA is 10cm as well. Find AG using the Pythagorean Theorem.
- [tex] (OG)^2 + (AG)^2 = (OA)^2 [/tex]
- [tex] (OG)^2 + (AG)^2 = (10cm)^2 [/tex]
» OB is also a radius, measuring 10cm. The difference of OB and BG is OG.
- [tex] OG = OB - BG [/tex]
- [tex] OG = 10cm - 2cm [/tex]
» OG is 8cm. Substitute it to our solution to find AG.
- [tex] (8cm)^2 + (AG)^2 = (10cm)^2 [/tex]
- [tex] 64cm^2 + (AG)^2 = 100cm^2 [/tex]
- [tex] (AG)^2 = 100cm^2 - 64cm^2 [/tex]
- [tex] (AG)^2 = 36cm^2 [/tex]
- [tex] \sqrt{(AG)^2} = \sqrt{36cm^2} [/tex]
[tex] \therefore [/tex] AG measures 6cm
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