If a parallelogram is cyclic, then it is a rectangle. Justify.

Using vector method, prove that if the diagonals of a parallelogram are equal, then it is a rectangle.

Show that the points A(1,2,3),B(-1,-2,-1),C(2,3,2) and D(4,7,6) are the vertices of a parallelogram ABCD, but it is not a rectangle.

Using dot product of vectors, prove that a parallelogram, whose diagonals are equal, is a rectangle

Placenta is an endocrine tissue. Justify.

Placenta is an endocrine tissue. Justify.

Placenta is an endocrine tissue. Justify.

Cronquist classification is a failure. Justify