Answer:
x ≈ 23.31
Step-by-step explanation:
We can use the law of cosines because we know 2 sides and 1 angle.
The general formula for the law of cosines if the triangle sides are a, b,c and α is the angle between sides a and b. c is the missing side.
[tex]c = \sqrt{a^{2} +b^{2} -2*a*b* cos \alpha }[/tex]
In our problem the law of cosines is
x = [tex]\sqrt{21^{2} +13^{2} - 2*21*13 *cos 83}[/tex]
x ≈ 23.31
