Expert: Jack Cheng - 11/28/2006

Question
can you help me i don't have a TI89 calculator

1). Find the value of:
 
   a. log sin 62°22'33"
   b. log cot 28°13'17"
   c. log cos 125°15'23"
   d. log tan 78°45'50"

2). Find the acute angle A, to the nearest second, when:
   
    a. log cos A=9.12575
    b. log sin A=9.91655
    c. log cot A=0.11975
    d. log tan A=0.06323


Answer
Hi John,

Sorry that I took so long. I was out for a while.

You don't need a graphing calculator for this, only scientific calculator with the log and trig functions.

1) You first have to convert the minutes and seconds into decimals. Then simply apply the decimal in degrees to the sin function. 22' is equaled to 22/60 degrees and 33'' is equaled to 33/3600 degrees.

See if that helps, if not I'll you an example.

2) You first have to solve for cos A first (or sin or tan), then do the inverse trig function. To get rid of the log (here I am assuming the natural log), do e^ to both sides.

I have never seen problems like these, i.e. with the log and then a trig function.

http://www.sundials.co.uk/tbcal.htm

somehow says that you can just ignore the log, but I did not read deep enough to find out.

I hope this helps.

Jack