If tan θ =20/21, then the value of (sinθ-cosθ)/(sinθ+cosθ) is :

tan θ = \(\frac{20}{21}\)

{ tan θ = \(\frac{P}{B}\) }

Now,

\(\frac{sinθ - cosθ}{sinθ + cosθ}\)

= \(\frac{P - B}{P + B}\)

= \(\frac{20 - 21}{20 + 21}\)

= \(\frac{-1}{41}\)