# maths --plse help me..

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prove that the points (2,-1) (0,2) (2,3)and (4,0) are the coordinates of vertices of a parallelogram and find the angle between its diagonals

• maths --plse help me.. -

If we label the points ABCD as given, then

AB and CD have slope -3/2
AD and BC have slope 1/2
so, the sides are parallel

AC is vertical
BD has slope -1/2
so, tanθ = 2 ==> θ = 63.4°

The calculations are easier if you plot the points and draw the diagonals.

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