Question

Fast please. It's a math question. Here's the pic

Answer 1

Step-by-step explanation:

1) cos9@ - cos3@ = -2sin((9@+3@)/2)*sin((9@-3@)/2)

= -2sin6@sin3@

2)(sin7@-sin@)+(sin9@-sin3@)

=2sin((7@+3@)/2)cos((7@-3@)/2) + 2sin6@cos3@

=2sin5@cos2@ + 2sin6@cos3@

3)cos6@ + cos4@ + cos9@ + cos@

= 2cos(10@/2)cos(2@/2) + 2cos(10@/2)cos(8@/2)

=2cos5@cos@ + 2cos5@cos4@