Answer:

Explanation:
see the attached figure to better understand the problem
step 1
Find the length side KJ
In the right triangle JKM
Applying the Pythagoras Theorem

we have


substitute



simplify

step 2
Find the value of cosine of angle MJK in the right triangle JKM

substitute the values

simplify
-----> equation A
step 3
Find the value of cosine of angle MJK in the right triangle JKL

we have

----> remember equation A
substitute the values

Simplify
