双曲函数的性质
证明:
\[
\begin{aligned}
\sinh(x+y)=\sinh(x)\cosh(y)+\cosh(x)\sinh(y)\\
\sinh(x-y)=\sinh(x)\cosh(y)-\cosh(x)\sinh(y)\\
\cosh(x+y)=\cosh(x)\cosh(y)+\sinh(x)\sinh(y)\\
\cosh(x-y)=\cosh(x)\cosh(y)-\sinh(x)\sinh(y)\\
\end{aligned}
\]