Thursday, January 16, 2014

Verify the trigonometric identity square root [(1+sin x)/(1-sinx)]=(1+sinx)/|cosx|

We'll manage the left side of the expression and we'll
multiply the numerator and denominator by (1+sin x).


sqrt
[(1+sin x)^2/(1-sin x)*(1+sin x)] = (1+sinx)/|cosx|


We'll
recognize the difference of 2 squares at denominator:


sqrt
[(1+sin x)^2/[1- (sin x)^2]


We'll apply the Pythagorean
identity:


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


sqrt [(1+sin x)^2/[1- (sin x)^2] = |(1+sin x)^2|/|cos
x|


Since 1 + sin x >= 0 => |(1+sin x)| =
(1+sin x)


sqrt [(1+sin x)^2/[1- (sin x)^2] = (1+sin x)/|cos
x|


We notice that LHS = RHS, therefore the
identity sqrt [(1+sin x)^2/[1- (sin x)^2] = (1+sin x)/|cos x| is
verified.

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