Thursday, June 19, 2014

Verify the identity cscx+cotx=sinx/(1-cosx).

We'lll manage only the left side and we'll re-write the
terms of the sum:


csc x = 1/sin x and cot x = cos x/sin
x


csc x + cot x = 1/sin x + cos x/sin
x


Since the fractions have the same denominator, we can
write:


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


The expression will
become:


(1+cos x)/sin x = sin x/(1 - cos
x)


We'll cross multiply:


(sin
x)^2 = (1+cos x)(1-cos x)


The product from the right side
returns the difference of two squares:


(sin x)^2 = 1 - (cos
x)^2


We'll add (cos x)^2 both
sides:


(sin x)^2 + (cos x)^2 =
1


But Pythagorean identity states that (sin x)^2 + (cos
x)^2 = 1, therefore we've came up with a true
statement.


Therefore, the given identity csc
x + cot x = sin x/(1 - cos x) is verified.

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