Step 1: Recall the basic identity. For any angle, the squares of sine and cosine always add up to one. \[ \sin^2\theta + \cos^2\theta = 1 \]
Step 2: Check with real values. Here $\sin 30^\circ = \tfrac{1}{2}$ and $\cos 30^\circ = \tfrac{\sqrt{3}}{2}$. \[ \left(\tfrac{1}{2}\right)^2 + \left(\tfrac{\sqrt{3}}{2}\right)^2 = \tfrac{1}{4} + \tfrac{3}{4} = 1 \] So the value is one. \[ \boxed{1} \]