Question

the value of sin 21 * cos 9 + cos 159 * sin 189

Answer 1

Answer:

maybe right

Step-by-step explanation:

Multiplying it by 2 ,

=2sin21°cos9° – 2cos84°cos6°

=cos(21–9)°– cos(21+9)° – cos (84+6) –cos(84–6)

=cos 12° – cos30° – cos90° – cos78°

=cos(90–78)°–√3/2 – 0 – cos 78°

=sin78° –0.87–cos 78°

=0.97–0.87– 0.20

=–0.1