if cos2x = -1/49, find tanx for -3pi/2 < x < -pi

tips for any helpful replies, thanks

u could find the angle.. using cos inverse and dividing 2. and plug the angle u got into tan and see if its in between those ranges

This post was edited by FamilyGuyViewer on Mar 1 2014 07:14pm

cos(2x) = 2.cos(x)² - 1 = 1 - 2.sin(x)²

Given that cos(2x) = -1/49, plug in this value into the 2 formulas and solve for cos(x) and for sin(x), using the fact that -3pi/2 < x < -pi to help choosing between negative or positive square roots.

Then, form the quotient sin(x) / cos(x).

ty both, that helped