Math CentralQuandaries & Queries


Question from Tony, a student:

find the value of pi in the following:

sin pi= cos(pi + 40)

sin(80 - pi)=cos pi

your kind input is really appreciated

Hi Tony,

If you are trying to solve $\sin(x) = \cos(x + 40)$ then I suggest that you use the multiple angle formula for the cosine function to expand the right side. This will give you an equation involving $\sin(x)$ and $\cos(x).$ If you now divide both sides by $\cos(x)$ you will have an equation for $\tan(x)$ which you can solve for $x.$


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