Does a trig identity exist for $\displaystyle \frac{\sqrt{2}}{2}$ ?

In other words, can $\displaystyle \frac{\sqrt{2}}{2}$ be expressed in terms of $\displaystyle \sin\theta, \cos\theta...$ etc. just as 1 can be set equal to $\displaystyle \sin^2\theta+\cos^2\theta$ ?