Prove that:

2/3 cosec2 58°-2/3 cot 58° tan 32° -5/3 tan 13° tan 37° tan 45° tan 53° tan 77° = —1.

Consider L.H.S.

= cosec2 58°- cot 58° tan 32° - tan 13° tan 37° tan 45° tan 53° tan 77°


= cosec2 58°- cot 58° tan (90-58)° - × [tan 13° tan 77°] × [tan 37° tan 53° ] × tan 45°


= cosec2 58°- cot 58° cot 58° - × [tan 13° tan (90-13)°] × [tan 37° tan (90-37)° ] × 1


= cosec2 58°- cot2 58° - × [tan 13° cot 13°] × [tan 37° cot 37° ]×1


= [cosec2 58°- cot2 58°] - × [1] × [1] × 1


= [1] -


= (2/3) – (5/3)


= (2 - 5)/3


= -3/3


= -1 = R.H.S.


Hence, proved.


16