The diagonals of a parallelogram intersect at a 42◦ angle and have lengths of 12 and 7 cm. Find the lengths of the sides of the parallelogram. (Hint: The diagonals bisect each other.)

Answer 1

if the sides have length a and b,

a^2 = 6^2 + 3.5^2 - 2(6)(3.5)cos42
b^2 = 6^2 + 3.5^2 + 2(6)(3.5)cos42