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November 27, 2015
Posted by **kc** on Sunday, July 24, 2011 at 8:47pm.

- pre cal 2 -
**Reiny**, Sunday, July 24, 2011 at 11:00pmsin4x=-2sin2x

2 sin2xcos2x = -2sin2x, ......... since sin2A = 2sinAcosA

cos2x = -1

2x = 180°, 360°, 540°, 720° which is π , 2π 3π, or 4π radians

x = 90° ,180°,270°, 360° which is π/2, π , 3π/2, or 2π radians