Quadrilaterals ...

The quadrilateral formed by joining the mid-points of the sides $$AB,BC,CD,DA$$ of a quadrilateral $$ABCD$$ is

If $$ABC$$ is a triangle, right-angled at $$B$$ and $$M,N$$ are midpoints of $$AB$$ and $$BC$$ respectively, then what is $$4({AN}^{2}+{CM}^{2})$$ equal to?

$$ABC$$ is a triangle in which $$AB=AC$$. Let $$BC$$ be produced to $$D$$. From a point $$E$$ on the line $$AC$$ let $$EF$$ be a straight line such that $$EF$$ is parallel to $$AB$$. Consider the quadrilateral $$ECDF$$ thus formed. If $$\angle ABC={65}^{o}$$ and $$\angle EFD={80}^{o}$$, then what is $$\angle FDC$$ equal to?

Which of the following statements is INCORRECT ?

In the figure given, $$M$$ is the midpoint of the side $$CD$$ of the parallelogram $$ABCD$$. What is $$ON:OB$$?

The figure formed by joining the mid-points of the sides of a quadrilateral $$ABCD$$, taken in order, is a square only if,

The basic elements of a Quadrilateral are _____.

Which of the following statements is INCORRECT?

If length of each side of a rhombus $$PQRS$$ is $$8cm$$ and $$\angle {PQR}={120}^{o}$$, then what is the length (in cm) of $$QS$$?

$$ABCD$$ is a quadrilateral inscribed in a circle. Diagonals $$AC$$ and $$BD$$ are joined.
If $$\angle CAD = 60^{\circ}$$ and $$\angle BDC = 25^{\circ}$$. Find $$\angle BCD$$