What is the value of tan 0?

The value of tan 0 is 0. This is because the tangent function is defined as the ratio of the sine and cosine functions: tan(θ) = sin(θ)/cos(θ). At 0 degrees (or 0 radians), sin(0) is 0 and cos(0) is 1, resulting in tan(0) = 0/1 = 0.