1. **State the problem:** We are given the area of a square as 36 cm² and need to find the length of one side of the square. 2. **Formula used:** The area $A$ of a square is given by the formula $$A = s^2$$ where $s$ is the length of one side. 3. **Apply the formula:** Substitute the given area into the formula: $$36 = s^2$$ 4. **Solve for $s$:** Take the square root of both sides: $$s = \sqrt{36}$$ 5. **Calculate the square root:** $$s = 6$$ 6. **Interpret the result:** The length of one side of the square is 6 cm. **Final answer:** a. 6 cm