1) First draw line.
2) then draw a semi-circle on the line.
3) put compass on one end an mark an arc on the semi circle.
4) put compass on the newly made arc and made another arc against the 1st one.
5) now put compass on the 1st arc and make an arc above the semi circle.
6) now put compass on the second arc an cut the arc that we made above the semi circle.
7) join the base with the area where the 2 arcs cut each other.
8) now put compass on that area where the semi-circle and the dotted line meet and draw arc.
9) put the compasson that place from where u marked the very 1st arc, it shoul cut the last arc we made.
10) now join the intersecting point of the 2 arcs with the point on the base from where we started our dotted line.
here is the diagram (tried my best)...........
hope this will help u...........plzzz mark it as brainliest.........