# What goes in the gap?

Lara Alcock wrote about Tilting the Classroom in the London Mathematical Society Newsletter. One of the activities she does that I don’t do but should is what I’ll call What goes in the gap? from her section on deciding. The example she gives is which symbol of $\Longleftarrow$, $\Longrightarrow$, $\iff$ goes in the gap in

$(a_n)\to a\qquad (|a_n|)\to |a| .$

Clearly one can do this with many other statements not just symbolic ones

For $\Phi :R ^n \to R ^n$, $\Phi$ is orthogonal         $\Phi$ is an isometry.

Alcock recommends that students vote on the answers to encourage engagement and notes that sometimes multiple rounds of voting are required!