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Mathematics 19 Online
OpenStudy (juan1857):

Find the limit (if it exists)

OpenStudy (juan1857):

\[\lim_{x \rightarrow \frac{ \pi }{ 4 }} \frac{ 4x }{ tanx}\]

jimthompson5910 (jim_thompson5910):

what happens when you plug in x = pi/4?

OpenStudy (juan1857):

no idea

jimthompson5910 (jim_thompson5910):

\[\LARGE \lim_{x \to \frac{\pi}{4}}\frac{4x}{\tan(x)} = \frac{4*\left(\frac{\pi}{4}\right)}{\tan\left(\frac{\pi}{4}\right)}\] \[\LARGE \lim_{x \to \frac{\pi}{4}}\frac{4x}{\tan(x)} = \frac{\cancel{4}*\left(\frac{\pi}{\cancel{4}}\right)}{\tan\left(\frac{\pi}{4}\right)}\] \[\LARGE \lim_{x \to \frac{\pi}{4}}\frac{4x}{\tan(x)} = \frac{\pi}{\tan\left(\frac{\pi}{4}\right)}\] I'll let you simplify the rest. Use the unit circle to find the value of tangent.

jimthompson5910 (jim_thompson5910):

\[\Large \tan(\theta) = \frac{\sin(\theta)}{\cos(\theta)}\] \[\Large \tan\left(\frac{\pi}{4}\right) = \frac{\sin\left(\frac{\pi}{4}\right)}{\cos\left(\frac{\pi}{4}\right)}\] Use the unit circle to locate the angle pi/4. Then find the sine and cosine of that angle. Divide the two values

jimthompson5910 (jim_thompson5910):

Each point on the unit circle is of the form (x,y) where x = cos(theta) y = sin(theta)

OpenStudy (juan1857):

oh ok

OpenStudy (juan1857):

.76 and .65 ?

jimthompson5910 (jim_thompson5910):

or you can use a calculator like this one http://web2.0calc.com/ to compute `sin(pi/4)` and `cos(pi/4)` make sure you're in radian mode

OpenStudy (juan1857):

ok so after i do that what is next

jimthompson5910 (jim_thompson5910):

what did you get for `sin(pi/4)` and `cos(pi/4)`

OpenStudy (agent0smith):

"what happens when you plug in x = pi/4?" "no idea" Seems like you need to review some trig, or algebra.

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