Write the value of cos1∘+cos2∘+...+cos180∘.
cos1∘+cos2∘+...+cos180∘
=cos(180∘−179∘)+cos(180∘−178∘)+...+cos90∘+cos91∘+....+cos180∘
=−cos179∘−cos178∘−....−cos91∘+cos90∘+cos90∘+....+cos180∘
=cos90∘+cos180∘
=0-1
=-1
Write the value of cos 1° cos 2° cos ³° ...cos 179° cos 180°