Construct an isos

Step1: construct a segment BC with the length of 4.5 cm

Now we have to draw perpendicular bisector to BC because in an isosceles triangle the altitude from vertex point i.e. A is also the perpendicular bisector

Step2: take distance in compass greater than half of BC. Keep the needle of the compass on point C and draw arcs above and below BC

Step3: keeping the distance in the compass same as in the above step keep the needle of compass on point B and draw arcs intersecting the previous arcs above and below BC. Mark the intersection points of arcs as M and N

Step4: draw a line passing through points M and N and mark the intersection point with BC as point D

Step5: take distance 3.8 cm in compass keep the needle of compass on point D and mark an arc intersecting the line MN above BC. Mark this intersection point as A

Step6: draw segment AB and AC and required ΔABC is ready