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Integral of 1/(1+√tan x)

Short answer

Let I = ∫₀^{π/2} dx/(1+√tan x). Replace x by π/2−x to get I = ∫₀^{π/2} √sin x/(√sin x+√cos x) dx. Adding the two forms combines numerator and denominator, giving 2I = ∫₀^{π/2} dx = π/2, so I = π/4.

Evaluate: ∫₀^{π/2} dx/(1 + √tan x).

Let I = ∫₀^(π/2) dx/(1 + √tan x).

Write tan x = sin x/cos x, so 1 + √tan x = (√cos x + √sin x)/√cos x:

I = ∫₀^(π/2) √cos x/(√cos x + √sin x) dx

Replace x by π/2 − x (swap sin and cos):

I = ∫₀^(π/2) √sin x/(√sin x + √cos x) dx

Add the two forms:

2I = ∫₀^(π/2) (√cos x + √sin x)/(√sin x + √cos x) dx = ∫₀^(π/2) dx = π/2

I = π/4.

✓ Answer checked by Claude Opus 5.5 (high effort)

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