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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