<s>[INST] explain to me in a simple to understand way what the equation for finding the nth triangle number is and how it can be proved by using only high school level math. please give each step of a proof using LaTeX. [/INST] A triangle number is a number that is the sum of all the integers from 1 up to a given integer n. The equation for finding the nth triangle number is given by the formula:

\begin{equation}
T_n = \frac{n(n+1)}{2}
\end{equation}

To prove this formula, we can use mathematical induction:

Basis step: For n = 1, the equation gives us T1 = 1 * (1 + 1) / 2 = 1, which is the first triangle number.

Inductive step: Assume that the formula holds for n = k, i.e., T_k = k * (k + 1) / 2.

Now we need to prove that the formula also holds for n = k + 1, i.e., T_{k + 1} = (k + 1) * (k + 2) / 2.

\begin{align}
T_{k + 1} &= T_k + (k + 1) \
&= \frac{k(k + 1)}{2} + (k + 1) \
&= \frac{k^2 + k}{2} + \frac{2k + 2}{2} \
&= \frac{k^2 + 3k + 2}{2} \
&= \frac{(k + 1)(k + 2)}{2} \
&= T_{k + 1}
\end{align}

Therefore, the formula holds for n = k + 1 as well.

Conclusion: By mathematical induction, we have shown that the formula T_n = n * (n + 1) / 2 holds for all positive integers n. </s>