Consider the RHS

and use the addition formula for sine

can you continue?

Consider the LHScotA * sec˛A * sin˛A = tan A

change to

change to

can you continue?

Consider the RHS

(1 + sinA * cosA) (sinA - cosA) = sinłA - cosłA

use the formula for the difference of two cubes on to expand it

difference of two cubes formula:

can you continue?

Consider the right hand sidecscA = (secA + tanA) / (secA - cosA + tanA)

change to

change to

then combine all the fractions and simplify as much as possible

can you continue?