1. The problem asks for the probability of heads appearing on the 5th toss given that tails appeared on the first four tosses of a fair coin. 2. Each toss of a fair coin is independent, meaning the outcome of one toss does not affect the others. 3. The probability of heads on any single toss of a fair coin is always $\frac{1}{2}$. 4. Therefore, regardless of previous outcomes, the probability of getting heads on the 5th toss is simply $\frac{1}{2}$. Final answer: $\frac{1}{2}$.