Question

if A=60 and B =30 verify that cos (A-B) = cosA cosB +sinA sinB​

Answer 1

Since. A=60 and B=30 then,

Cos(A-B) = cos 30= ✓3/2

Now,

CosAcosB + sinAsinB=

= 1/2*✓3/2+✓3/2*1/2

=✓3/4+✓3/4

=2✓3/4

= ✓3/2=cosA

Hence verified.