Question

Sin80cos20+sin45cos145+sin55cos245

Answer 1

Answer:

cos 80 cos 20 + sin 45 cos 145 + sin 55 cos 24

  = 1 2 [ 2 cos 10 cos 20 + 2 sin 45 cos145 + 2 sin 55 cos 245 ]

= 1 2 [ cos ( 10 + 20 ) + cos ( 20 − 10 ) + sin ( 45 + 145 ) − sin ( 145 − 45 ) + sin ( 245 + 55 ) − sin ( 245− 55 ) ]

= 1 2 [ cos 30 + cos 10 +sin 190 − sin 100 + sin 300 − sin 190 ]

= 1 2 [ sin ( 90 − 30 ) + cos 10 − sin ( 90 + 10 ) + sin ( 360 − 60 ) ]

= 1 2 [ sin 60 + cos 10 − cos 10 − sin 60 ]

= 1 2 ⋅ 0

= 0

Step-by-step explanation:

Answer 2

Answer:

This is my answer .....SAYAN BANERJEE