Triangles question bank (Maths)

Fill in the blanks using the correct word given in brackets:
$(i)$ All circles are $........$ (congruent,similar)
$(ii)$ All squares are $.........$ (similar,congruent)
$(iii)$ All $.........$ triangles are similar. (isosceles,equilateral)
$(iv)$ Two polygons of the same number of sides are similar,if $(a)$ their corresponding angles are $......$ and $(b)$ their corresponding sides are $......$ (equal,proportional)

$ABCD$ is a trapezium with $AB \parallel DC.$ $E$ and $F$ are points on non-parallel sides $AD$ and $BC$ respectively such that $EF \parallel AB$ (see Figure). Show that $\frac{AE}{ED} = \frac{BF}{FC}$.