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3 (iii)   Verify the following: (–1, 2, 1), (1, –2, 5), (4, –7, 8) and (2, –3, 4) are the vertices of a parallelogram.

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 Given A=(–1, 2, 1), B=(1, –2, 5), C=(4, –7, 8) and D=(2, –3, 4)

Given Three points  A=(0, 7, –10), B=(1, 6, – 6) and C=(4, 9, – 6)

The distance between two points (x_1,y_1,z_1) and (x_2,y_2,z_2) is given by

d=\sqrt{(x_2-x_1)^2+(y_2-y_1)^2+(z_2-z_1)^2}

The distance AB

AB=\sqrt{(1-(-1))^2+(-2-2)^2+(5-1)^2}

AB=\sqrt{4+16+16}

AB=\sqrt{36}

AB=6

The distance BC

BC=\sqrt{(4-1)^2+(-7-(-2))^2+(8-5)^2}

BC=\sqrt{9+25+9}

BC=\sqrt{43}

The distance CD

CD=\sqrt{(2-4)^2+(-3-(-7))^2+(4-8)^2}

CA=\sqrt{4+16+16}

CA=\sqrt{36}

CA=6

The distance DA

DA=\sqrt{(-1-2)^2+(2-(-3))^2+(1-4)^2}

DA=\sqrt{9+25+9}

DA=\sqrt{43}

Here As we can see 

AB=6=CA And BC=\sqrt{43}=DA

As the opposite sides of quadrilateral are equal, we can say that ABCD is a parallelogram.

Posted by

Pankaj Sanodiya

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