Question

cos 340°.cos 40° + sin 200°.sin 140°​

Answer 1

Answer:

cos 340 * cos 40 + sin 200 * sin 140

cos(360-20)*cos40+sin(180+20)*sin(180-40)

cos20*cos40+(-sin20)*sin40

cos20*cos40-sin20*sin40

cos A * cos B - sin A * sin B = cos(A+B)

so, cos(40+20)= cos60 = 0.5

Step-by-step explanation:

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