**Q) **If sin θ – cos θ = 0, then find the value of sin^{4} θ + cos^{4} θ.

**Ans: **Since sin θ – cos θ = 0

sin θ = cos θ

hence tan θ = 1 and θ = 45^{0}

and hence sin 45^{0 } = cos 45^{0} =

sin^{4} θ + cos^{4} θ

= sin^{4} 45 + cos^{4} 45

= +

= +

=