(1 - cosx) (1 + 1/cosx) = sinxtanx

cos x ≠ 0 ⇔ x ≠ ; k ∈ N

<=> cos²x + sin²x = 1

⇔ 1 = 1

=> x =  { R \ (pi/2 + k.pi); k ∈ N}

Step-by-step explanation:

the multiples of 15 are 15, 30,45, 60, 75, 90, 105, 120, 135, 150, 165, 180, 195,   210, 225, 240, 255, 270, 285, 300, 315, 330, 345, 360, 375,   390, 405, 420, 435, 450, 465, 480, 495, 510, 525, 540, 555, 570, 585, 600, 615, 630, 645, 660, 675, 690, 705, 720, and 735.

the factors of 15 are 1, 3, 5, and 15.

hope that , fam!

-une, your fren : )