sqrt(x^2 - 49)/x where x = 7 sec(theta)

sqrt(7(sec(theta)))^2 - 49) / (7sec(theta))

sqrt(49(sec(theta))^2 - 49)/ (7sec(theta))

sqrt(49[(sec(theta))^2 - 1]) / (7sec(theta))

sqrt{49(tan(theta))^2 / (7sec(theta))

(7 tan(theta)) / (7sec(theta))

7 tan(theta) cos(theta)/ 7

tan(theta) cos(theta)

sin(theta)/cos(theta) * cos(theta)

sin(theta)