Look at the Picture and Fill in the Blanks

79:

Look at the picture and fill in the blanks.

In the figure, O is the centre of a circle.

(a)The line segments , and are the radii.

(b) is the diameter.

80:

Look at the picture and fill in the blanks.

In the figure, O is the centre of a circle.

(a) is the diameter, which is the longest line segment inside the circle.

(b)The length of OE is half of .

(c) , and are the radii.

84:

Answer the following question.

In the circle below, O is the centre.

Which line segment is the diameter of the circle?

The line segment is the diameter of the circle.

85:

Colour the circumference of the circle below in green.

86:

Colour the circumference of the circle below in green.

499

Look at the picture and answer the questions.

(a)Which point is the centre?

Point ( A / B / C / D ) is the centre.

(b)Which line segment is the diameter? Why?

500

The figure below is a circle with O as the centre.

(a)Have a measure and complete the table below.

(b)Among the line segments in the figure, is the longest. Since it passes through the , it is the of the circle.

(c)OD, OE, and are radii of the circle because they are line segments that are joined to the and the circumference. Besides, their lengths are of the diameter.

(d)The length of CD is the same as those of OA and OC. They are

cm long. However, CD is not the radius of the circle because it is not joined to the .

(e)OCD is an triangle. AOE is an triangle.

501

Look at the circle below and complete the following.

(a)Have a measure. The diameter of the circle above is cm.

(b)Find the position of the centre of the circle using a straight ruler and mark it with ‘×’.

502

Look at the circle below and complete the following.

(a)Have a measure. The diameter of the circle above is cm.

(b)Find the centre using a straight ruler and mark it with a ‘×’.

377:

Draw line segments inside the circle according to instructions.

(a)Draw the diameter AB.

(b)Draw two radii OC and OD.

378:

Draw line segments to find the position of the centre of the circle and mark the position with ‘×’. Then measure the diameter.

379:

Draw line segments to find the position of the centre of the circle and mark the position with ‘×’. Then measure the diameter.

380:

Draw line segments to find the position of the centre of the circle and mark the position with ‘×’. Then measure the diameter.

381:

In the figures below, A, B and C are the centres of three circles respectively. Have a measure and then calculate.

(a)The radius of the circle with A as the centre is cm.

The radius of the circle with B as the centre is cm.

The radius of the circle with C as the centre is cm.

(b)Find the lengths of AB, BC and AC.

+ = .

The length of AB is cm.

+ = .

The length of BC is cm.

+ = .

The length of AC is cm.

(c)What kind of triangle is triangle ABC?

Triangle ABC is an triangle.

382:

In the figure below, D and F are the centres of the two circles respectively. Have a measure.

(a)The radius of the small circle is cm long.

The radius of the large circle is cm long.

(b)DE is cm long.

EF is cm long.

FG is cm long.

DG is cm long.

(c)The perimeter of this quadrilateral is cm.