Convert your into sin and cosFor , starting with LHS,
how do i continue?
Then you'll want to make this into one fraction and since the LCM is we'll use that.
As these have the same denominator we can combine fractions so the above is equal to
You should know that from your double angle identities that and you should also know that when dividing by a fraction we flip it and multiply.
From the definition of sec: so that cancels to leave and again from the definition of sec:
Since this is equal to the RHS we've proved the identity is true