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we are on proving identities in trigonometry and i dont understand this

sec + csc
---------- == sec
1 + cot

how do i get one side equal to the other, can you explain to me???

2007-12-11 08:10:54 · 2 answers · asked by molly 1 in Science & Mathematics Mathematics

2 answers

Pull out a common sec out of the numerator:

sec + csc
-------------
1 + cot

sec(1 + csc/sec)
-----------------------
1 + cot

Now notice that csc = 1/sin and sec = 1/cos

So csc/sec = 1/sin / 1/cos

This is the same as cos/sin which is also the same as cot

Finally you get:
sec( 1 + cot )
-------------------
(1 + cot)

Now you can cancel the 1 + cot to get:

sec

QED

2007-12-11 08:19:08 · answer #1 · answered by Puzzling 7 · 1 0

sec(x) = 1/cos(x)
csc(x) = 1/sin(x)
cot(x) = cos(x)/sin(x) = csc(x)/sec(x)

LHS
= (sec(x) + csc(x)) / (1 + cot(x))
= (sec(x) + csc(x)) / (1 + csc(x)/sec(x))
= sec(x)(sec(x) + csc(x)) / (sec(x) + csc(x))
= sec(x)
= RHS

2007-12-11 08:16:14 · answer #2 · answered by gudspeling 7 · 0 0

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