Question

Help with evaluating a fraction!

Answer 1

\[-\frac{ 1 }{ 8\cos ^{3}(t) }|t=\frac{ \pi }{ 4 }\]

Answer 2

please show work as obviously I can enter it into a calculator if I just want the answer.

Answer 3

go to www.wolframalpha.com, besides answer, it will show u steps and graphs

Answer 4

that is what i use all the time

Answer 5

not helpful. but thanks

Answer 6

\[\frac{ -1 }{ 8(\frac{ \sqrt{2} }{ 2 })^3}=\frac{ -1 }{ 8(\frac{ 2\sqrt{2} }{ 8 }) }=...?\]

Answer 7

this is how I am trying to solve this. \[=-\frac{ \sqrt{2} }{ 4 }\] is the correct answer.. but I cannot figure out for the life of me how to get there.

Answer 8

\[\Large\bf\sf -\frac{1}{8\left(\cos t\right)^3}\quad=\quad -\frac{1}{8\left(\cos \frac{\pi}{4}\right)^3}\quad=\quad -\frac{1}{8\left(\frac{\sqrt2}{2}\right)^3}\]

Answer 9

So I see you posted some steps, where are you getting stuck?

Answer 10

\[\Large\bf\sf -\frac{1}{2\sqrt2}\]Rationalize ( get the irrational sqrt2 out of the denominator ) by multiplying top and bottom by sqrt2,\[\Large\bf\sf -\frac{1}{2\sqrt2}\left(\frac{\sqrt2}{\sqrt2}\right)\quad=\quad -\frac{\sqrt2}{2\cdot2}\]

Answer 11

Was it just the last step that you didn't understand?

Answer 12

yes!

Answer 13

sorry was dealing with other things. Thank you Zep!