Question

(2*cos^2 (68) -1) / (2*cos(113)*sin(67))

Answer 1

cos(2*68)/(2cos180-67)*sin67)=cos136/(-2cos67*sin67)=
=-cos136/sin134=-cos(180-44)/sin(90+44)=cos44/cos44=1

Answer 2

cos(2*68) это откуда?

Answer 3

2cos^2(a)-1=cos2a