Verify the identity: cos x sin x tan x = sec x.

this isn't true. For a counter example, let x = pi/4.
So sin x cos x tan x = 1/2, but sec x = sqrt of 2.

Marie Ridge,

If cos x. sin x. tan x = sec x
cos x.sin x . Sin x/cos x = sec x
sin x. sin x = sec x
sin ~2 x = sec x

Try further, and if it does not help, write here. I am ready to help you, but you must show what you have calculated so far, and from what I suggest, what did you find, now?

The display is not correct, sometimes the plus sign misses unless the "math" environment is used.

The correct assertion is

\cos x+\sin x\tan x=\frac{1}{\cos x}

which is easily solved by multiplying both sides by \cos x and using \cos x\tan x=
\sin x , \cos^2x+\sin^2x=1 .