why does the solution go from square root 7 tan theter to square root 7 then square root sec squared theter minus 1

X dx 7 sec 0 7 sec tan odo -7= 7 sec 0-7 =S= 7 sec7 sec tan odo 7 tan e = sec Odo 7 tan 0+C =sec 0-1+C = -1+C since x = 7 sec 7 = x-7+C dx=x-7+C