I came across this new symbol while reading a document about writing proofs, and I have never seen it before.
[Math] the symbol $\triangleq$
notation
notation
I came across this new symbol while reading a document about writing proofs, and I have never seen it before.
Best Answer
It’s is defined to be equal to; it’s my preferred symbol, but the most common one is $:=$, and I’ve also seen $\overset{\text{def}}=$.
The $\triangleq$ indicates that $\mathscr{U}$ is being defined to be $\{U_x:x\in X\}$: we are not saying that some previously defined $\mathscr{U}$ is equal to the collection of these sets $U_x$.