Question

ii) cos40° cos 100° cos160º = }​

Answer 1

Answer:

cos40° cos 100° cos160º cos 220°

Answer 2

Answer:

1/8

Step-by-step explanation:

cos40 cos 100 cos  160

= 1/2 * 2cos40 cos 100 cos  160

= 1/2 * (2cos160 cos 40) cos 100

= 1/2 * (cos 200 + cos 120 ) cos 100

= 1/4 * [ (2cos200 cos 100) + (2cos 120 cos 100) ]

= 1/4 *[ (cos 300 + cos 100) + 2*(-0.5)*cos100 ]

= 1/4 * cos 300

= 1/4 * cos 60

= 1/8