length of remaining side?

Question

Two sides of a triangle have lengths 5 and 11 and the angle between them is 1/4π. What is the length of the remaining side?

(Give a decimal approximation correct to at least two decimal places.)

Answer 1

Using the Law of Cosines and calling the missing side x, we have:

x² = 5² + 11² - 2(5)(11)cos( π/4 )