Question

cos40°cos20°-sin40°sin20°;2)cos70°cos40°+sin70°sin40°​

Answer 1

$\cos(40) \cos(20) - \sin(40) \sin(20) = \cos(40 + 20) = \cos(60)$

$\cos(70) \cos(40) + \sin(70) \sin(40) = \cos(70 - 40) = \cos(30)$