Intersecting Lines and Non-intersecting Lines

Draw four pairs of intersecting lines. Check by actual measurements whether vertically opposite angles are equal or not?

In the adjacent figure slant line $t$ intersects the two lines $l$ and $m$ at points $P$ and $Q$ respectively. If $\angle 2=\angle 3=90°$ then prove that line $l$ and $m$ are mutually parallel. What will be value of $\angle 1+\angle 3?$

In the adjacent figure $l\parallel m, p\perp m$ and $p\perp n$

(i) Is $m\parallel n ?$ why $?$ 

(ii) Is $l\parallel n?$ why $?$

(iii) Is  $p\perp l ?$ why $?$

$ABCD$ is a square and $L,M,N$ and $O$ are the midpoints of the sides $AB,BC,CD$ and $DA$ respectively. Measure the angles and sides observe that shape $LMNO$ is also a square.

$ABCD$ is a trapezium in which $AD\Vert$ $\mathrm{BC}$. Line segments $BL$ and $CM$ are perpendicular to the line $AD$. Show that $BL\Vert CM$ , if $BC=BL$ then show that $BCML$ is a square.

In the given figure, $15$ every angle of quadrilateral $ABCD$ is right angle. Prove that $AB\parallel CD$ and $AD\parallel BC$.

Draw a lines $PQ \& RS$ intersecting at point $O$. Measure a pair of vertically opposite angles. Bisect them. Are the bisecting rays forming a straight line?

Define parallel lines and transversal. Also, state the properties of angles by a transversal when it intersects two parallel lines at different points.

Three or more lines are _____, if they pass through a common point.