# Find and angle between 0 and 2pi that is coterminal with the angle given by - 77pi/5

• Apr 15th 2009, 10:39 PM
mathstupid
Find and angle between 0 and 2pi that is coterminal with the angle given by - 77pi/5
find an angle between 0 and 2pi that is coterminal with the angle given by -77pi/5

thanks! much appreciated
• Apr 15th 2009, 11:17 PM
Twig
$\displaystyle \frac{-77 \pi}{5} = -15 \pi -\frac{2 \pi}{5}$

Angle coterminal with $\displaystyle -\frac{2 \pi}{5} \mbox{ is } \frac{8 \pi}{5}$
• Apr 16th 2009, 12:08 AM
mathstupid
sorry but can you explain that a bit because my math teacher is really picky about the work we show.

shouldnt it be:

-77pi/5 + 2pi + 2pi + 2pi + 2pi + 2pi + 2pi + 2pi + 2pi = 3pi/5 ?
• Apr 16th 2009, 08:45 AM
Twig
oops, yeah sry, $\displaystyle \frac{3\pi}{5}$ is right.

$\displaystyle \frac{-77\pi}{5} = -15\pi -\frac{2\pi}{5}$ (You can check this).

Now $\displaystyle -15\pi$ is "being at the same place" as just $\displaystyle \pi$ .

So being at pi, $\displaystyle \frac{5\pi}{5} - \frac{2\pi}{5} = \frac{3\pi}{5}$