Question

plz try to explain the step after multiplying it both side by 1-sin@ and then the 3rd step.

Answer 1

see...
after multiplying i-sin@ to numerator and denominator
we get
cosA (1-sinA) / (1+cosA) (1-sin^2A)
now,
1-sin^2A = cos^2A........see in denominator
therefore we get,
cosA (1-sinA) / (1+cosA) cos^2A
now
separate 1/cos^2A and rest part
we get
1/cos^2A × cosA(1-sinA)/ (1+cosA)

here see the right part
we can bring cosA to denominator of (1+cosA)
because ultimately we will get same ...

therefore we can write it as
1/cos^2A × (1-sinA)/(1+cosA)/cosA
then write
1/cos^2A × (1-sinA)/ ( 1/ cosA+ cosA/cosA )

then
1/ cos^2A × ( 1- sinA) / ( sec A + 1)
then proceed as given in solution.......

hope u understand...