First we'll find this diagonal marked d.



Let's erase the upper half of the parallelogram:



Now we have SAS, so we use the law of cosines:











Now we go back to the original parallelogram.
Two adjacent angles of a parallelogram are
supplementary, so since 180° - 50° = 130°



Next we'll find this diagonal marked d'.



Let's erase the upper half of the parallelogram:



Again we have SAS, so we use the law of cosines again:











Edwin