Answer:
see explanation
Step-by-step explanation:
Using the trigonometric identities
sin²Θ = 1 - cos²Θ , cos²Θ = 1 - sin²Θ
Consider the left side
(sinΘ + cosΘ)(1 - sinΘcosΘ) ← distribute
= sinΘ(1 - sinΘcosΘ) + cosΘ(1 - sinΘcosΘ)
= sinΘ - sin²ΘcosΘ + cosΘ - sinΘcos²Θ
= sinΘ - (1 - cos²Θ)cosΘ + cosΘ - sinΘ(1 - sin²Θ)
= sinΘ - cosΘ + cos³Θ + cosΘ - sinΘ + sin³Θ ← collect like terms
= sin³Θ + cos³Θ
= right side ⇒ proven
