Writing a formula means to fill the empty list with letters, figures and mathematical symbols. That is straightforward: use your keyboard. As soon as you type something the empty symbol will vanish and you will see whatever you have inserted instead. New characters are always put at the current cursor position.
Escreber unha fórmula significa preencher a lista valeira con letras, e símbolos matemáticos. Isto é simples: use o teclado. En canto escreba algo o símbolo de valeiro ha desaparecer e verá o que teña inserido. Os novos carácteres son postos sempre na posición do cursor.