Answer:
-4sinθcosθ
Step-by-step explanation:
Note:
1. (a + b)^2 = a^2 + 2ab + b^2
2. (a - b)^2 = a^2 - 2ab + b^2
3. sin^2θ + cos^2θ = 1
(sinθ -cosθ)^2 - (sinθ + cosθ)^2
= sin^2θ - 2sinθcosθ + cos^2θ - (sin^2θ + 2sinθcosθ + cos^2θ)
= sin^2θ + cos^2θ - 2sinθcosθ - (sin^2θ + cos^2θ + 2sinθcosθ)
= 1 - 2sinθcosθ - (1 + 2sinθcosθ)
= 1- 2sinθcosθ -1 - 2sinθcosθ
= - 2sinθcosθ - 2sinθcosθ
= -4sinθcosθ
