Final answer:
True, Mizar is a complex star system and is a true example of a double spectroscopic binary, consisting of Mizar A and Mizar B, both being spectroscopic binaries on their own.
Step-by-step explanation:
True, Mizar is indeed an example of a double spectroscopic binary. This complex star system consists of Mizar A and Mizar B, both of which are themselves spectroscopic binaries. This means that each of these components is made up of two stars that orbit each other so closely that they can't be distinguished visually through a telescope.
The presence of these companions was deduced through spectral analysis of their light curves and changes in their absorption lines. Edward C. Pickering, observing the spectrum of Mizar, noticed that the lines changed and sometimes doubled, evidence that Mizar A was a binary star system. Likewise, other spectroscopic binaries such as Algol exhibit similar properties.
In addition to being a double spectroscopic binary, Mizar forms an optical pair with Alcor, visible without a telescope and known for centuries. However, Alcor and Mizar do not orbit each other but merely appear close together from our perspective, forming an optical double.