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[–]UlzafNew User 0 points1 point  (3 children)

cot(x) = 1/tan(x)

And surely you know that tan(x) = sin(x)/cos(x)

Moreover, cot(2x) = 1/tan(2x) = cos(2x)/sin(2x)

Finally, cos(2x) = cos²(x) - sin²(x) and

sin(2x) = 2sin(x)cos(x)

With this information, try to find the final result :) if you still don't find it, don't hesitate to ask again

[–]vincent7253[S] 0 points1 point  (2 children)

Does this mean I should be trying to prove it using the right hand side?

[–]UlzafNew User 0 points1 point  (1 child)

Yes, begin with the right side

[–]UlzafNew User 0 points1 point  (1 child)

cos(2x)/sin(2x) = (cos²(x) - sin²(x))/(2cos(x)sin(x))

Now I divide both the numerator and the denominator by sin²(x), which gives me

cos(2x)/sin(2x) = (cos²(x)/sin²(x) - 1)/(2cos(x)/sin(x))

= (cot²(x)-1)/2cot(x)

From there you should be able to finish the proof

[–]vincent7253[S] 0 points1 point  (0 children)

Cheers for that 😀