umm...trigonometry?

Test Preparation
1

<p>could someone please tell me if this is right</p>

<p>(sec^2)(x) = 4(tan^2)(x)</p>

<p>(sec^2)(x) = 4<a href="sec%5E2">(sec^2)(x) - 1</a>(x) = 4(sec^2)(x) - 4
-3(sec^2)(x) = -4
(sec^2)(x) = 4/3
sec(x) = 2/(sqrt3)
cos(x) = (sqrt3)/2
x = (pi/6)+2(n)(pi), (11pi/6)+2(n)(pi)</p>

<p>thanks</p>

2

<p>"(sec^2)(x) = 4/3
sec(x) = 2/(sqrt3)"</p>

<p>You need a +/-</p>

<p>"cos(x) = (sqrt3)/2
x = (pi/4)+2(n)(pi), (7pi/4)+2(n)(pi)"</p>

<p>cos(pi/4) = (sqrt2)/2; cos(pi/6) = (sqrt3)/2</p>

<p>Easier way:</p>

<p>(sec^2)(x) = 4(tan^2)(x)
1/(cos^2)(x) = 4 (sin^2)(x)/(cos^2)(x)
1 = 4 (sin^2)(x)
(sin^2)(x) = 1/4
sin(x) = +/- 1/2
x = pi/6 + npi, 5pi/6 + npi</p>