A triangle has sides a=1 and b=5 and angle C=40 degrees. Find the length of side c.

Answer 1

This looks like a Law of Cosines Problem

Use the formula

c²=a²+b²-2abcosC

c²=(1)²+(5)²-2(1)(5)cos40

c²=1+25-10cos40

c²=26-7.66=18.33955557

Square root both sides and

c=4.3