Exercise 15.1
Page-15.5Question 1:
Fill in the blanks:
(i) All points lying inside/outside a circle are called ........ points /.......points.
(ii) Circles having the same centre and different radii are called ...... circles.
(iii) A point whose distance from the centre of a circle is greater than its radius lies in ......of the circle.
(iv) A continuous piece of a circle is ....... of the circle.
(v) The longest chord of a circle is a ....... of the circle.
(vi) An arc is a ..... when its ends are the ends of a diameter.
(vii) Segment of a circle is the region between an arc and ....of the circle.
(viii) A circle divides the plane, on which it lies, in ...... parts.
Answer 1:
(i) interior/exterior
(ii) concentric
(iii) the exterior
(iv) arc
(v) diameter
(vi) semi-circle
(vii) centre
(viii) three
Question 2:
Write the truth value (T/F) fo the following with suitable reasons:
(i) A circle is a plane figure.
(ii) Line segment joining the centre to any point on the circle is a radius of the circle.
(iii) If a circle is divided into three equal arcs each is a major arc.
(iv) A circle has only finite number of equal chords.
(v) A chord of a circle, which is twice as long is its radius is a diameter of the circle.
(vi) Sector is the region between the chord and its corresponding arc.
(vii) The degree measure of an arc is the complement of the central angle containing the arc.
(viii) The degree measure of a semi-circle is 180°
Answer 2:
(i) Given that a circle is a plane figure.
As we know that a circle is a collection of those points in a plane that are at a given constant distance from a fixed point in the plane.
Thus the given statement is 
.
(ii) Given that line segment joining the centre to any point on the circle is a radius of the circle.
As we know that line segment joining the centre to any point on the circle is a radius of the circle.
Thus the given statement is .
(iii) Given that if a circle is divided into three equal arcs each is a major arc.
As we know that if points P, Q and R lies on the given circle C(O, r) in such a way that
Then each arc is called major arc.
Thus the given statement is .
(iv) It is given that a circle has only finite number of equal chords.
As we know that a circle having infinite number of unequal chords.
Thus the given statement is
.
(v) Given that a chord of the circle, which is twice as long as its radius is diameter of the circle.
As we know that a chord of a circle which is largest to others and passing through the centre of the circle and twice as long as its radius is called diameter of the circle.
Thus the given statement is .
(vi) It is given that sector is the region between the chord and its corresponding arc.
As we know that the region between the chord and its corresponding arc is called sector.
Thus the given statement is.
(vii) Given that the degree measure of an arc is the complement of the central angle containing the arc.
As we know that the degree measure of a minor arc is the measure of the central angle containing the arc and that of a major arc is 360° minus the degree measure of the corresponding minor arc.
Let degree measure of an arc 
is θ of a given circle 
is denoted by 
Thus the given statement is.
(viii) Given that the degree measure of a semi-circle is 180°.
As we know that the diameter of a circle divides into two equal parts and each of these two arcs are known as semi-circle.
and 
are semi circle
Hence,
Thus the given statement is.
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