Complex number alternative notation

Question

I have seen the following notation for a complex number in a book on digital signal processing:

$$c = M\angle \phi$$

Did anyone see such notation before and how to interpret it?

Answer 1

I have never seen it before, but my guess is that $M\angle\phi$ means $M\bigl(\cos(\phi)+i\sin(\phi)\bigr)$.

Answer 2

You can notice there is the angle sign ($\angle$) before $\phi$, so the autor intends to use angles. In particular this type of notatoon is the same as: $$c=Me^{i\phi }=M(\cos(\phi)+i\sin(\phi))$$ Or, in other words the complex number of mudulus $M$ and $arg(c)=\phi$