To calculate the unknown side of a triangle, I need to know if this is a right triangle or not. If it is a right triangle, we can apply the Pythagorean theorem. For other types of triangles, we would use different methods like the Law of Sines or the Law of Cosines.

Please provide the measurements (sides or angles) for the triangle, or upload an image so I can better understand the problem.

Let me know if you would like more details on these methods! Also, here are five relative questions that could expand on this information:

1. How do you apply the Pythagorean theorem in non-right triangles?
2. Can you calculate the length of a side using only the angles?
3. What is the Law of Sines, and when is it used?
4. How do you derive the Law of Cosines for any triangle?
5. How do angles affect the side lengths in any triangle?

Tip: For right triangles, the Pythagorean theorem is an efficient tool to find unknown sides when two sides are known.