Verify That Each Equation Is an Identity $$\cos ( 4 \theta ) = \cos ^ { 4 } \theta - 6 \sin ^ { 2 } \theta \cos ^ { 2 } \theta + \sin ^ { 4 } \theta$$

question 19

Essay

Verify that each equation is an identity.
- $$\cos ( 4 \theta ) = \cos ^ { 4 } \theta - 6 \sin ^ { 2 } \theta \cos ^ { 2 } \theta + \sin ^ { 4 } \theta$$

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