cos130° cos40°+ sin130° sin40° is
1
0
1/2
Not defined
By using the identity
cos(x - y) = cosx cosy + sinx siny , we have
cos130° cos40°+ sin130° sin40°= cos(130°-40°)= cos( 90°) = 0
cos130° cos40° + sin130° sin40° is equal to
sin70∘+cos40∘cos70∘+sin40∘=
1) Sin(40+A)cos(10+A)-cos(40+A)sin(10+A)