Problema Solution
cos(190°) cos(15°) - sin(190°) sin(15°)
Answer provided by our tutors
since cos(A + B) = cos A cos B − sin A sin B we have
cos(190°) cos(15°) - sin(190°) sin(15°) = cos(190° + 15°) = cos(205°) = cos(180 + 25) = - cos(25) = - 0.90630779