Answer:
See below.
Step-by-step explanation:
Write the sec's as 1 / cos and the tan's as sin / cos
I will write sin as s and cos as c:
Left side = 1 / ( cos)a - b) = 1 / (ca cb + sa sb)
Right side = 1 / ( ca cb ( 1 + sa sb / ca cb))
= 1 / ( ca cb * ( ca cb + sa sb) / ca cb)
The 'ca cb' cancels out so
Right side = 1 / (ca cb + sa sb) = left side..
