Supposing that we have to prove that
(sinA+cosB)/(sinA-cosB) = (secB+cscA)/(secB-cscA), we'll cross multiply and we'll
get:
(sinA+cosB)(secB-cscA) =
(sinA-cosB)(secB+cscA)
We'll pu sec B = 1/cos B and sec B
= 1/cos B
csc A = 1/sin A and sec A = 1/cos
A
We'll substitute secA,secB,cscA and cscB inside
brackets:
(sinA+cosB)(1/cos B - 1/sin A) =
(sinA-cosB)(1/cos B + 1/sin A)
We'll remove brackets using
FOIL method:
sinA/cosB - sinA/sinA + cosB/cosB - cosB/sinA
= sinA/cosB + sinA/sinA - cosB/cosB - cosB/sinA
sinA/cosB
-1 + 1- cosB/sinA = sinA/cosB + 1- 1 - cosB/sinA
We'll
eliminate like terms and we'll get LHS =
RHS:
sinA/cosB - cosB/sinA = sinA/cosB -
cosB/sinA
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