(a) 120°
The below given steps will be followed to construct an angle of 120°.
(1) Draw a line 1 and mark a point P on it. Now taking P as centre and with a convenient radius, draw an arc of a circle which intersects line l at Q.
(2) Taking Q as centre and with the same radius as before, draw an arc intersecting the previously drawn arc at R.
(3) Taking R as centre and with the same radius as before, draw an arc intersecting the arc at S (see figure).
(4) Join PS, which is the required ray making 120° with line l.
(b) 45°
The below given steps will be followed to construct an angle of 45°.
(1) Draw a line l and mark a point P on it. Now taking P as centre and with a convenient draw an arc of a circle which intersects line l at Q.
(2) Taking Q as centre and with the same radius as before, draw an arc intersecting the previously drawn arc at R.
(3) Taking R as centre and with the same radius as before, draw an arc intersecting the arc at S (see figure).
(4) Taking R and S as centres, draw arcs of same radius to intersect each other at T.
(5) Join PT. Let it intersect the major arc at point U.
(6) Taking Q andU as centres, draw arcs with radius more than QU to intersect each other at V. Join PV.
PV is the required ray making 45° with the given line l.
(c) 135°
The below given steps will be followed to construct an angle of 135°.
(1) Draw a line l and mark a point P on it. Now taking P as centre and with a convenient radius, draw a semi circle which intersects line l at Q and R.
(2) Taking R as centre and with the same radius as before, draw an arc intersecting the previously .drawn arc at S.
(3) Taking S as centre and with the same radius as before, draw an arc intersecting the arc at T (see figure).
(4) Taking S and T as centre, draw arcs of same radius to intersect each other at U.
(5) Join PU. Let it intersect the arc at V. Now taking Q and V as centres and with radius more than QV, draw arcs to intersect each other at W.
(6) Join PW which is the required ray making 135° with line l.
