Question

Please explain your answer!

Answer 1

Explanation:

tan x = ( sin x ) / ( cos x )

tan²x + 1 = sec²x

sec x = ± √(tan²x + 1)

sec x = 1 / cos x

~~~~~~~~~~~~

tan x = 4 and sin x < 0

cos x - ?

If tan x > 0 and sin x < 0 ⇒ cos x < 0

sec²x = 16 + 1 = 17 ⇒ cos²x =
`(1)/(17)`

cos x = -
`(√(17) )/(17)`