Question

(tgt+ctgt)^2-(tgt-ctgt)^2

Answer 1

(tgt+ctgt)^2-(tgt-ctgt)^2=tg^2t+2×tgt×ctgt+ctg^2t-tg^2t+2×tgt×ctgt-ctg^2t=4×tgt×ctgt=
4×sint/cost×cost/sint=4