Question

15.BOC is a diameter of a circle with centre O. If AB and
CD are two chords such that AB || CD and AB = 10 cm,
then CD =
5 cm
12.5 cm
15 cm
10 cm​

Answer 1

Answer:

SOLUTION

(d) 10 cm

Draw OE ⊥ AB and OF ⊥ CD.

In Δ OEB and ΔOFC, we have:

OB = OC (Radius of a circle)

∠BOE = ∠COF (Vertically opposite angles)

∠OEB = ∠OFC (90° each)

∴ ΔOEB ≅ ΔOFC (By AAS congruency rule)

∴ OE = OF

Chords equidistant from the centre are equal.

∴ CD = AB = 10 cm

Step-by-step explanation:

pls mark me as brainlist friend

Answer 2

Answer:

75° ans

Step-by-step explanation:

Given :BC=OB and angle ACD=25°

here in angle OBC

angle BOC + angle BCO+ angle OBC = 180°

25°+25°+ angle OBC=180°

50° + angle OBC= 180°

angle OBC =108°- 50°

•

• • angle OBC = 130°

Here

ABC=ABO+OBC=180°

ABO +130°=180°

ABO= 180°-130°

•

• • ABO = 50°

Now, in angle AOB

OB=OA ( radius )

ABO= BAO = 50° [ angles opposite to equal side are equal

By angle sum property

ABO+BAO+AOB = 180°

50°+50°+ AOB= 180°

AOB =180° - (50°+ 50°) = 180°- 100 °= 80°

•

• • AOB= 180°

Here

DOC= AOD+ AOB+ BOC = 180°

AOD+ 80°+ 25°= 180°

AOD+ 105°=180 °

AOD= 180°- 105°

AOD= 75°

•

• • AOD = 75°