To solve the integral of √(25+x²), the substitution x = 5tan(θ) is recommended. This transformation simplifies the expression, allowing the use of the identity ∫sec(θ) dθ = ln|sec(θ) + tan(θ)| + C for evaluation. The problem relates to the Pythagorean theorem, suggesting a connection between the integral and trigonometric identities. Factoring out a 5 from the square root leads to the expression 5√(1 + (x/5)²), reinforcing the substitution. This approach provides a clear pathway to finding the integral without needing arcsinh.