posted by ashley -- .
The lengths of 2 adjacent sides of a parallelogram are 42 cm and 36cm. an angle of the parallelogram is 4o degrees. Find the measure of the longest diagonal to the nearest tenth of a centimeter.
The longest diagonal forms a triangle with 180°-40°=140° and adjacent sides of 42 and 36 cm.
Using the cosine rule:
=73.32 cm (approx.)