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.