help math level 2 buffs!

Test Preparation
1

<p>hey, i was working thru my math level 2 practice test today and i realized i have no clue as to how to solve one type of question with radian values. here it goes:</p>

<p>if cos x = tan x, which of the following is a possible radian value of x?</p>

<p>(A) -1.00
(B) -0.52
(C) 0.00
(D) 0.52
(E) 0.67</p>

<p>Please help!</p>

2

<p>cosx = sinx/cosx</p>

<p>cos^2 x = sinx</p>

<p>1-sin^2 x = sinx</p>

<p>sin^2 x +sinx -1 = 0</p>

<p>Graph; root is ~.67</p>

3

<p>sinx/cosx = cosx
sinx = (cosx)^2
sinx = 1-(sinx)^2
(sinx)^2 - sinx -1 = 0
completing the square gives
(sinx+0.5)^2 - 0.5^2 - 1 = 0
(sinx+0.5)^2 = 1.25
sinx = root1.25 - 0.5</p>

<p>taking the positive root, inverse sine and you will get 0.67</p>

<p>Now answer my thread lol :P</p>

4

<p>couldn't you also just plug all those into your calculator?</p>

5

<p>yeppers....</p>

6

<p>how come when I do cos(.67) and tan(.67) they come out to different values.?</p>

<p>I get cos(.67) = .78 and tan(.67) = .79</p>

7

<p>the discrepancy is probably due to the rounded figure (More Exact- .66624...)</p>

8

<p>anyways the .01 difference between cosx and tanx when plugging in .67 is the smallest difference out of all the other choices, so that would be the right answer.</p>