# missing angle

• January 31st 2011, 06:26 AM
andyboy179
missing angle
hi, can you check if im right when trying to find the missing angle of this shape?

Attachment 20645

to work this out i did this:

inverse tan 7/11= 7.44???

is this correct? if not where am i going wrong?

thanks!
• January 31st 2011, 06:38 AM
how did you calculate $tan^{-1}(7/11)$ (and state whether radians or degrees)
• January 31st 2011, 06:43 AM
andyboy179
on my calculator i just wrote " tan^-1 7/11= 7.44

my calculator is in degrees!
• January 31st 2011, 06:48 AM
Ackbeet
Your calculator, due to the lack of parentheses, computed $\tan^{-1}(7)/11,$ not $\tan^{-1}(7/11).$ Try that again, and see what you get. This is what BAdhi was getting at, I think. Incidentally, you were right to doubt the correctness of the result. You should always have a rough idea of what a calculator is going to give you.
• January 31st 2011, 06:50 AM
andyboy179
okay, so i nned to do $\tan^{-1}(7)/11,$ = 32.47??
• January 31st 2011, 06:54 AM
Ackbeet
Right answer, wrong typing. You should have

$\tan^{-1}(7/11)\approx 32.47^{\circ}.$
• January 31st 2011, 06:59 AM
e^(i*pi)
Some models require the argument first. If this is the case type $7 \div 11$ and then inverse tan button