cos5 cos6 sin5 sin6 The angle of elevation of the top of a

cos(5) cos(6) - sin(5) sin(6) The angle of elevation of the top of a water tower from point A on the ground is 17.9 degree. From point B, 70.0 feet closer to the tower, the angle of elevation is 36.8 degree. What is the height of the tower?

Solution

d. cos 5 cos 5-sin5 sin6

This is of the form cos A cos B - sinA sinB which is equal to cos(A-B)

therefore cos5 cos6-sin5 sin6=cos(5-6)=cos(-1)

and cos(- theta)=cos theta

Therefore cos(-1)=cos 1

and that\'s the answer.