The value of tan[cos−1(−27)−π2] is
23√5
3√52
2√5
None
tan[cos−1(−27)−π2]=tan[π−cos−1(27)−π2]=tan[π2−cos−1(27)]=cot(cos−1(27))=cot(cot−1(2√45))=2√45=23√5
The value of cos[2tan−1(7)] is