sin10+sin20+sin30+sin40cos10+cos20+cos30+cos40=
tan520
tan30
tan40
tan50
We have sinα+sinα+d+.....sinα+n−1dcosα+cosα+d+.....cosα+n−1d=sinα+α+n−1d2cosα+α+n−1d2
∴sin1∘+sin2∘+sin3∘+sin4∘cos1∘+cos2∘+cos3∘+cos4∘=sin1+42ocos1+42o=tan52o