ENGN 103 ENGINEERING DRAWING GEOMETRIC CONSTRUCTIONS LECTURE 2

ENGN 103 ENGINEERING DRAWING GEOMETRIC CONSTRUCTIONS LECTURE 2

DRAW AND MARK THE DIMENSIONS: • • • Circle of Radius 30 mm. And mark the radius. Circle of diameter 25 mm. Mark the diameter. Rectangle of length 100 mm and breadth 60 mm. Square of side 40 mm. Triangle of sides 80 mm, 65 mm and 60 mm. Triangle of side 65 mm and angle 55 degree and 70 degree. • Hexagon of sides 40 mm.

• • • Draw a line of 65 mm and bisect the line. Draw a line of 70 mm and divide into 5 equal parts. Draw a line of 90 mm and divide in a ratio of 3: 4 Draw an angle of 75 degree and bisect the angle. Draw an arc and find the center of the arc. Construct a triangle of sides 75 mm, 65 mm and 70 mm. Inscribe a circle inside the triangle. Mark the radius. • Construct a triangle of sides 35 mm, 40 mm and 55 mm. Circumscribe a circle around the triangle. Mark the radius. • Construct an ellipse of major axis 70 mm and minor axis 40 mm.

• To bisect a line • Draw the given line AB, with centers A and B and radius R greater than half of AB, draw arcs to intersect a t C and D. Join CD, when E will be the mid point of the line. Also CD will be perpendicular to AB

A B

A B

A B

C A B D

• To bisect an angle • Draw the given angle ABC and from the apex B draw an arc of radius R to cut AB and CD at D and E. R may be any convenient radius. With D and E as centers and radius R’, draw two arcs to meet F. Again, R’ may be any convenient radius. Join FB to bisect the angle.

A B C

A D B E C

A D B E C

A D B E C

A O D B E C

• To inscribe a circle in a triangle. • Draw the given triangle ABC and bisect an two angles. Produce the bisectors to intersect at O, which is the center of the inscribe circle.

• To draw the circumscribing circle of a triangle. • Draw the given triangle ABC. Bisect any two of the sides and produce the bisectors to intersect at O. O is the center of the circumscribing circle.