# How To do tan^-1 on a calculator

First off, I’m assuming that your calculator has three things: a “tan” button and a “tan-1” button. You do not have to know where the “tan-1” button is, but if it is a scientific calculator then it probably does have it. I’m also assuming that you know what the “tan” and the “tan-1” buttons do, so this will not explain that.
______________________________________________________________________
Your calculator should have a button labeled “tan-1”, although usually you have to hit the “2nd” key and then the “tan” key. If you are using the calculator that comes installed with Windows 7 (at least I’m pretty sure that’s where it comes from, if someone could verify that please) and already have it set to scientific calculator (hit the “view” button in the top left corner then select “scientific”), then you hit the “Inv” key (short for “Inverse”, I think) and the “tan” button will turn into “tan-1”.
Also, make sure that the calculator is set to degrees (or radians), because it is extremely frustrating to get the wrong answer and have no idea why. To set that there is often a button that says “DRG”, with which you can cycle through degrees, radians, and gradients, using arrow keys if your calculator has them. On the Windows 7 calculator there are three buttons in the top left, beneath where the output is shown. Click the one labeled with what you want.
Finally, if you already know how to get the “tan-1” button but don’t know how to type it in, most fancy calculators (the \$10+ ones) require you to input the items in the order that you would write them (e.g. type “tan-1” then “500” then “/” then “1001” then “=”). However, almost every other calculator that I use (including the Windows 7 one and calculator apps) do it similarly, but certain functions (such as square root, log, and tan) are done after you finish typing the expression (e.g. type “500” then “/” then “1001” then “tan-1” then “=”).
Of course, all of this also applies to the “sin”/”sin-1” and “cos”/”cos-1” buttons, but I was specifically asked about the “tan-1” button, so that’s what I went with.
~ George

# How To Randomly Choose A Winner Using Only A Watch

Do you ever need an easy, random way to choose who among you and your friend(s) can go first? Just look at your watch.

##### How To Replicate A Coin Flip With A Watch

My friend and I often have trouble deciding who goes first. We usually end up doing some sort of coin toss, but (over) half the time we don’t have coins. This is my solution: I’ve only tried this with a digital watch, but I’m sure it could be applied to analog watches too in some way (I’ll update this if I can think of how). Have the other person choose Even or Odd. Then look at your watch’s seconds (or minutes, if necessary). If the number is even then whoever chose even wins, and if the number is odd then whoever chose odd wins. Simple as that.

##### How To Choose A Winner From A Small Group of People Without Checking Your Watch More Than Twice

The basis of the randomization process is the seconds on your digital watch (or the seconds hand on your analog watch). Give everyone a number, starting with one and working your way up from there. Then check your watch and see how many seconds have passed since the last minute.

• If there are…
• 2 people and number of seconds that have passed is below 30, then person #1 wins. Otherwise he loses
• 3 people and number of seconds that have passed is below 20 then person #1 wins, if the number is equal to or above 40 then person #3 wins, and otherwise person #2 wins
• 4 people, do the same thing as with three people, only the seconds are split into four areas, 0-14, 15-29, 30-44, and 45-59
• 5 people, analog watches would have a harder time, but digital watches’ would have the five areas be 0-11, 12-23, 24-35, 36-47, and 48-60
• 6 people, it should be obvious if you’ve read this far, just divide 60 by 6
• 7 people, I don’t know yet
• 8 people, then split the group into two groups of four and check your watch, selecting one person from both groups at once. Then check your watch again to see who of the two of them wins
• 9 people, split the group into three groups of three and check your watch. Pick the winner from each group and check your watch again using the method for three people
• 10 or 12 people , instead of giving each person 6 seconds give them each five, that way it would work for an analog watch
• For greater numbers, try dividing 60 by the number, breaking them into groups, or using my next suggestion which I came up with while writing this one
##### How To Choose A Winner From A Large Group Using A Watch (Or A Coin)

Have everybody pick 1 or 2 (this would also work with heads or tails). Decide if 1 equals odd or even, and decide that 2 is the other. Check your watch, and say which group stays based on which number they picked. Keep doing this until there is only one person left, and if everybody goes out in one round then have a do-over. If everybody keeps picking the same thing, try having them pick between other numbers, letters, or even colors, and keep switching up what they have to choose from.

~ George