the diagonals of a parellelogram are 20 cm and 30cm long and intersect at an angle of 25 degrees. Find the sides of the parellelogram
the diagonals intersect each other so let's consider the triangle of sides 15 and 10 with the contained angle of 25 degrees
by the cosine law you can find the third side, which will be one of the sides of the parallelogram.
x^2 = 15^2 + 10^2 - 2(15)(10)cos 25
= 53.10766
x = 7.28
Do the same with the other side by using sides 15, 10 and angle 155