Question

sin21°cos9°−cos84°cos6°=​

Answer 1

Step-by-step explanation:

sin21 cos9-cos84 cos6

sin21 cos9-cos (90-6)cos6

sin21cos9-sin6cos6

1/2 (2sin21cos9-2sin6cos6)

1/2 {sin (21+9)+sin (21-9)}-1/2{sin(6+6)+sin (6-6)}

1/2 {sin30+sin12}-1/2 {sin12+sin0}

1/2 {1/2+sin12}-1/2 {sin12+0}

1/4+1/2sin-1/2sin12

1/4 answer