Question

if Cos (a + b)= 20 then sin( a - b )can be reduced to......

option a cos b
option B cos 2b
opt c sin a
opt d. sin 2a

please explain the steps also please please please

Answer 1

as cos(a+b)=0
this implies a+b=90degress
that is a and b are complementary
I don't know if it is correct I have tried if wrong u can report and delete it
as per me ur ans is option b

Answer 2

cos(a+b) =0
a+b = 90
a = 90-b
put in given equation
sin(a-b) = sin ( 90-b-b)
= sin ( 90-2b )
= cos(2b)

hope it will help you!!