Question

the adjacent sides of parallelogram are 21 cm and 28 cm if its one diagonal is 35 cm; find the area of the parallelogram

Answer 1

Answer:

Step-by-step explanation:

Area of the parallelogram = l × b

= 21*28

= 588 cm^2

Answer 2

Area of the parallelogram=2× Area of triangle made by adjacent sides and diagonal

Semi perimeter of triangle=a+b+c/2(a,b and c are sides of triangle)
=21+28+35/2=84/2=42 cm
Area of triangle= √s(s-a)(s-b)(s-c)
=√42(42-21)(42-28)(42-35)
=√42×21×14×7
=√2×7×3×3×7×2×7×7
=2×7×7×3
=294 cm^2
Now, area of parallelogram=2× area of triangle
=2×294
=588 cm^2
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