Verify That Each Equation Is an Identity $$\sec ^ { 4 } x - \tan ^ { 4 } x = \sec ^ { 2 } x + \tan ^ { 2 } x$$

Verify that each equation is an identity.
- $$\sec ^ { 4 } x - \tan ^ { 4 } x = \sec ^ { 2 } x + \tan ^ { 2 } x$$