3. (8th "Hope Cup" Senior High School Competition) The number of real roots of the equation $\cos x=x+\sin x$ is
A. 1
B. 2
C. 3
D. 4
3. A transforms the given equation $\cos x=x+\sin x$ into $-x=\sin x-\cos x=\sqrt{2} \sin \left(x-\frac{\pi}{4}\right)$. Its graph is roughly shown in Figure 4-1 as follows: