Below is the graph of a trigonometric function. It intersects its midline at $\left(\frac{2}{3} \pi, 1.2\right)$, and it has a minimum point at $\left(\frac{4}{3} \pi,-3.4\right)$. What is the amplitude of the function?

Please directly answer the question and provide the final value, e.g., 1, 2.5, 300.
Question: Below is the graph of a trigonometric function. It intersects its midline at $\left(\frac{2}{3} \pi, 1.2\right)$, and it has a minimum point at $\left(\frac{4}{3} \pi,-3.4\right)$. What is the amplitude of the function?

Please first conduct reasoning, and then answer the question and provide the final value, e.g., 1, 2.5, 300, at the end.
Question: Below is the graph of a trigonometric function. It intersects its midline at $\left(\frac{2}{3} \pi, 1.2\right)$, and it has a minimum point at $\left(\frac{4}{3} \pi,-3.4\right)$. What is the amplitude of the function?
