Math Help

Test Preparation SAT Preparation
1

<p>I can't get this trig identity... Any help out there?</p>

<p>tan^2 (x) - sin^2 (x) = tan^2 (x) * sin^2 (x)</p>

2

<p>tan^2(x) - sin^2(x) = tan^2(x)*sin^2(x)</p>

<p>( sin^2(x)/cos^2(x) ) - sin^2(x) =
( sin^2(x)/cos^2(x) ) - ( ( sin^2(x)<em>cos^2(x) ) / cos^2(x) ) =
( sin^2(x) - sin^2(x)</em>cos^2(x) ) / cos^2(x) =
( sin^2(x)<em>(1 - cos^2(x) ) ) / cos^2(x) =
( sin^2(x)</em>sin^2(x) ) / cos^2(x) =
tan^2(x)*sin^2(x) = </p>

<p>Hope that's right, I haven't done identities in a while.</p>

3

<p>An alternative way to do it:</p>

<p>Set y = sin^2(x), for simplicity. Then,</p>

<p>LHS = (y/(1-y)) - y = (y - y + y^2) / (1-y) = y^2 / (1-y) = RHS</p>