Final Answer
Step-by-step Solution
Specify the solving method
Starting from the left-hand side (LHS) of the identity
Using the cosine of a sum formula: $\cos(\alpha\pm\beta)=\cos(\alpha)\cos(\beta)\mp\sin(\alpha)\sin(\beta)$, where angle $\alpha$ equals $x$, and angle $\beta$ equals $y$
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$\cos\left(x-y\right)+\cos\left(y-x\right)$
Learn how to solve trigonometric identities problems step by step online. Prove the trigonometric identity cos(x-y)+cos(y-x)=2cos(x)cos(y)+2sin(x)sin(y). Starting from the left-hand side (LHS) of the identity. Using the cosine of a sum formula: \cos(\alpha\pm\beta)=\cos(\alpha)\cos(\beta)\mp\sin(\alpha)\sin(\beta), where angle \alpha equals x, and angle \beta equals y. Using the cosine of a sum formula: \cos(\alpha\pm\beta)=\cos(\alpha)\cos(\beta)\mp\sin(\alpha)\sin(\beta), where angle \alpha equals y, and angle \beta equals x. Combining like terms \cos\left(x\right)\cos\left(y\right) and \cos\left(y\right)\cos\left(x\right).