Mark the Correct alternative in the following:

cos 35o + cos 85o + cos 155o =


cos 35° + cos 85° + cos 155°


= 2 + cos 155°


= 2cos 60° cos 25° + cos (180°-25°)


= 2 1/2 cos 25° - cos 25°


= cos 25° - cos 25°


= 0 (Ans)

1