Question

show that cos(60-a)cos(30-b)-sin (60-a) sin(30-b)=sin(a+b)​

Answer 1

Answer:

Step-by-step explanation:

cos(60-a)cos(30-b)-sin (60-a) sin(30-b)

let A = 60-a ; B = 30-b

=> CosACosB - SinASinB (∵Cos(A-B) = cosACosB - SinASinB)

=> Cos(A+B)

=> Cos(60-a+30-b)

=> Cos(90 - (a+b))   (∵cos(90-θ) = Sinθ)

=> Sin(a + b)    

Hence proved