Find Value of Sin and Cos using Fingers
Today I am going to share with you a special memory trick for trigonometry, mailed to me by Debasis Basak – a young Class IX follower of QuickerMaths.com
By this method we can find out Sines and Cosines of different angles. It just requires your hand. Let’s understand this trick step by step -
Step 1
First mark the angles of 0, 30, 45, 60, and 90 on little, ring, middle and pointer finger and thumb of your left hand.
Step 2
On the palm of your left hand write the equation (x)^1/2 /2 or square root of x/2
Step 3
On the left will be cosine and on the right will be sine. You will understand why you need to do this in the next step with an example
Step 4
Suppose, you want to find Cos30
Fold the finger representing 30. i.e. ring finger of your left hand palm.
Count the numbers of fingers on the left of the ring finger, as per step 3. So since there are 3 fingers, x=3; put the value in the equation given in step 2
Hence, Cos30 = square root of 3/2
and Sin30 will be (sq. root of 1 /2) = 1/2
I appreciate the efforts of Debasis in sharing this trick with all of us. In case you want to share some quick calculation trick or technique, mail it to me at vineetpatawari [at] gmail [dot] com
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September 3rd, 2012 - 15:53
can u plz post some more examples how to calculate sin and cos values by fingers?
December 23rd, 2012 - 22:33
plz contact on 8386822000
February 15th, 2013 - 13:04
i’ve a question. please help me solve it.
two consecutive numbers are given to A and B. when A is asked ‘do you know B’s number?’ A denies. when B is asked whether he knows A’s no., B also denies. at the very moment, A replies that he knows B’s number. what may be B’s number?
options were-
a) 1 b) 2 c) 3 d) 8
July 10th, 2012 - 11:17
interesting posts
June 14th, 2012 - 13:19
When you say bend the ring finger the left side has one finger left and on the right side there are 3 fingers. It works for 30 and 90 well but not for all.
Though the efforts are nice
June 14th, 2012 - 13:16
Hello
The formula falls flat when one need to find the value of sin60 and sin 45.
September 18th, 2012 - 12:21
it works man
April 17th, 2012 - 23:20
Excellent!!!
March 27th, 2012 - 19:00
Very educative. Really it is interesting.
March 27th, 2012 - 09:25
nice idea…. i tried it nd got 2 knw smthng new
March 26th, 2012 - 23:56
how is tan found out and what about sin,how is it found out, is it counting the fingers from your right
March 26th, 2012 - 22:00
Nice article…Keep posting such good article
March 26th, 2012 - 21:59
Its a nice article shared…..Good work…
March 26th, 2012 - 14:48
Certainly a very good Idea; works perfect for at least sine and cosine functions;
However, I didn’t found any glitch in it.
equation is: x=sqrt(x)/2 and not sqrt(x/2).
Perfectly fine for me.
March 26th, 2012 - 14:31
It is certainly a good idea. But there is a small glitch. Sin 30 is 1/2 while Cos 30 is (sqrt 3) /2. The sqrt applies only to 3 and not to 2.
Similarly for 45, both sin and cos is 1 / (sqrt 2).
Needs a bit of tweaking?
April 4th, 2012 - 18:25
no sir , there is no need of tweaking. in sin 30 as you said , when you bend the the ring fnger 30 degrees you know that cos 30 is sqrt 3 /2 for sin please see the fingers lefton the right side . it is 1 therefore sin30 is sqrt1/2 or 1/2