If cos⁡ x=−4/5, and 180°<x<270°, what is tan⁡(2x)?

Question

Help please...................

Answer 1

Hi Raquel,

There's a double angle formula for tan(2x). It's a special case of the formula for the tangent of the sum of 2 angles: tan(x+y) = [tan(x) + tan(y)] / [1 - tan(x)tan(y)]. Just set x = y and you will have it!