Answer:
Step-by-step explanation:
Let's label this triangle as triangle ABC. Side AB is 18, side BC is 20 and side CA is 25 and the angle we are looking for is angle C. Use the Law of Cosines to find the missing angle. You have to use the Law of Cosines because in order to use the Law of Sines you have to have an angle given and we don't so we have no other options. In our case,
which for us looks like this:
and
and
and
and
Use the 2nd button and the cos button to find the missing angle.
Angle C = 45.4 which is, rounded to the nearest degree, 45°