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 -
First mark the angles of 0, 30, 45, 60, and 90 on little, ring, middle and pointer finger and thumb of your left hand.
On the palm of your left hand write the equation (x)^1/2 /2 or square root of x/2
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
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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