how to use a log book to find natural sines and natural cos ?

Let’s understand it using an example.

Find value of tan28

^{0}36^{/}Use the natural tangent table for this.

Step 1: first locate the 28˚ in first degrees column.

Step2: then, locate 36َ in next columns ranging from 0

^{/}to 54^{/}.The coinciding point will give you the value of tan28

^{0}36^{/}which is 0.5452.Find the value of tan72

^{0}28^{/}As there is no column of 28

^{/}We first find the value of tan72

^{0}28^{/}and then add the mean difference of 4^{/}.i.e. value of tan72

^{0}28^{/}(follow above steps)Now, add 4

^{/}value from mean difference column in 72˚ row i.e. 129.The answer will be 3.1524 + 129 = 3.1653

In the similar way you can find the value of sine and cosine using natural sine and natural cosine tables.

Hope, this method is clear to you.

Best wishes!

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