在这个公式中，每个字母都代表不同的数学符号。

In this formula, each letter stands for a different mathematical ___symbol.

数学中，'+'是表示加法的符号。

In math, the '+' ___symbol represents addition.

白鸽常被视为和平的象征。

The white dove is often seen as a ___symbol of peace.

交通警察用手势指挥车辆通行。

The traffic officer used hand ___symbols to direct the vehicles.