Question

if 5 sin 0 -7 cos0=0 then find the sec0

Answer 1

5 sin0 = 7cos0
Hence
5 tan0 = 7 (because we divide by cos0 both sides)

tan0 = 7/5
Using formula,
tan^20 + 1 = sec^2
49 + 25 = 25 sec^20
sec0 = √74 / 5

Answer 2

you need to learn trigonometry identities from your book