Question

(i) sin(A + B) sin(A – B) = sin2 A – sin2 B
(ii) cos(A + B) cos(A – B) = cos2 A – sin2 B = cos2 B – sin2 A
(iii) sin2(A + B) – sin2(A – B) = sin2A sin2B
(iv) cos 8θ cos 2θ = cos2 5θ – sin2 3θ​

Answer 1

Answer:

(i) sin(A + B) sin(A – B) = sin2 A – sin2 B

(ii) cos(A + B) cos(A – B) = cos2 A – sin2 B = cos2 B – sin2 A

(iii) sin2(A + B) – sin2(A – B) = sin2A sin2B

(iv) cos 8θ cos 2θ = cos2 5θ – sin2 3θ​

Step-by-step explanation:(i) sin(A + B) sin(A – B) = sin2 A – sin2 B

(ii) cos(A + B) cos(A – B) = cos2 A – sin2 B = cos2 B – sin2 A

(iii) sin2(A + B) – sin2(A – B) = sin2A sin2B

(iv) cos 8θ cos 2θ = cos2 5θ – sin2 3θ​

Answer 2

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