Draw an angle of 40°. Copy its supplementary angle.

The below given steps will be followed to construct an angle of 40º measure and the copy of its supplementary angle.

(1) Draw a line segment and mark a point O on it. Place the centre of the protractor at point O and the zero edge along line segment.

(2) Mark a point A at 40º. Join OA. OA is the required ray making 40º with. Ð POA is the supplementary angle of 40º.

(3) Draw an arc of convenient radius in the interior of Ð POA, while taking point O as centre. Let it intersect both rays of Ð POA at point B and C.

(4) Draw a line *m* and mark a point S on it. With the same
radius as used before, again draw an arc while taking point S as
centre. Let it cut the line *m* at point T.

(5) Now, adjust the compasses up to the length of BC. With this radius, draw an arc while taking T as centre, which will intersect the previously drawn arc at point R.

(6) Join RS. RS is the required ray which makes the same angle with
line *m*, as the supplementary of 40º is 140º.

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