Write two such things which are at right angles to each other.

Draw a line segment $AB$ of length $4 cm$, a point $O$ is taken on the line segment $AB$, such that $AO=1 cm$ and $OB=3 cm$. Now at $O$, draw a perpendicular $MO$ on $AB$ at $O$ with the help of a set square.

A line segment $PQ$ of length $4 cm$ is drawn. A point $O$ is taken on the line segment $PQ$. With the help of scale and pencil compass, draw a perpendicular $OM$ on $PQ$ at $O$.

A line segment $XY$ of length $5 cm$ is drawn. A point $P$ is taken outside the line segment $XY$. With a set square, draw a perpendicular $PL$, on line segment $XY$ from the point $P$.

A line segment $AB$ of length $8 cm$ is drawn. A point $P$ is taken on the line segment $AB$, so that $AP=3 cm$ and $BP=5 cm$. Draw a perpendicular $PL$ on the line segment $AB$, at point $P$ with the help of scale, pencil and a compass.

A line segment $AB$ of length $6 cm$ is drawn. Take a point $K$ outside this line segment. With the help of scale and compass draw a perpendicular $KL$ on the line segment $AB$.

Draw a triangle $ABC$ with the help of scale and pencil. From three vertices $A, B$ and $C$ of the triangle, perpendicular $AP, BQ$ and $CR$ are drawn on the sides $BC, AC$ and $AB$ respectively. Let's see from the figure, if the line segment $AP, BQ$ and $CR$ are concurrent i.e, they intersect at a point.

With the help of set square draw a right-angled triangle $ABC$ such that $\angle ABC=90°$. From the point $B$, draw a perpendicular on the hypotenuse $AC$. Also find, if the perpendiculars from $A, B$ and $C$, on the opposite side, meet at a point. If so, name the point.