How do you deal with Sqrt(3)/2?

[UrshumMurshum]

So often times when I'm going through TBR you get problems involving Cos(30) or Sin(60) and that gets you the Sqrt[3]/2. Dividing 2 is fast and simple, but Sqrt(3) gives you the awkward 1.73 to deal with.

I haven't yet tried doing percentages, but I think a possible faster way would be Sqrt(3)/2 is approximately .9 so you deduct 10% off your number.

Example

87 * Sqrt(3)/2 is approximately 87 * .9 which is 87 - 8.7 (8.7 being 10% of 87) which is just under 80. Although in reality Sqrt(3)/2 is .86 so you're off 4% on your calculation.

Yes this is a serious question, just wondering how anyone else does it?

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[shaggybill]

Just round and approximate. Add or subtract small amounts to make up the difference. The answer should be apparent from the choices given.

 

[MD Odyssey]

I know that it's 0.86. The same as I know that 1/sqrt(2) is 0.7 and that sqrt(2) is 1.4.

I'm being facetious - I have no idea how I do it. I just do maths and it all works out in the end.

 

[dmf2682]

Just round and approximate. Add or subtract small amounts to make up the difference. The answer should be apparent from the choices given.

This. It's a bit less than 1. Or around 7/8 if you need something better.

 

[Erythropoietin]

So often times when I'm going through TBR you get problems involving Cos(30) or Sin(60) and that gets you the Sqrt[3]/2. Dividing 2 is fast and simple, but Sqrt(3) gives you the awkward 1.73 to deal with.

I haven't yet tried doing percentages, but I think a possible faster way would be Sqrt(3)/2 is approximately .9 so you deduct 10% off your number.

Example

87 * Sqrt(3)/2 is approximately 87 * .9 which is 87 - 8.7 (8.7 being 10% of 87) which is just under 80. Although in reality Sqrt(3)/2 is .86 so you're off 4% on your calculation.

Yes this is a serious question, just wondering how anyone else does it?

Sqrt of 3 is 1.7
Sqrt of 2 is 1.4

Valentine's day is on 2/14
St. Patrick's day is on 3/17

Those are your shortcuts and you can divide from there 🙂

 

[dmf2682]

Sqrt of 3 is 1.7
Sqrt of 2 is 1.4

Valentine's day is on 2/14
St. Patrick's day is on 3/17

Those are your shortcuts and you can divide from there 🙂

Nice one.

 

[HerbalPlz]

Sqrt of 3 is 1.7
Sqrt of 2 is 1.4

Valentine's day is on 2/14
St. Patrick's day is on 3/17

Those are your shortcuts and you can divide from there 🙂

This is the best advice, here's some more info relating to this:

a square root trick I learned recently that could be helpful for trig problems

sqrt 1 = 1 (as in 1/1 = New Year's Day)
sqrt 2 = 1.4 (as in 2/14 = Valentine's Day)
sqrt 3 = 1.7 (as in 3/17 = St. Patrick's Day)
sqrt 4 = 2(0) (need I explain...?)

Source = http://forums.studentdoctor.net/showthread.php?t=528674&highlight=Arithmetic+Tips+Tricks