# Double-angle and half-angle

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Given tanx = 2 and the quadrant is 1.

Identify sin2x, cos2x, and tan2x using the double-angle and half-angle formulas.

https://brainmass.com/math/trigonometry/double-angle-half-angle-4344

#### Solution Preview

Double-Angle formula

Tan(2x)=2tan(x)/(1-tan(X)^2)=2*2/(1-2^2)= -4/3

Since angle X is in quadrant 1, we know that 2X is in quadrant 2 ...

#### Solution Summary

This shows how to use the double-angle and half-angle formulas.

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