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Question

# Find an example to show that, in general, each statement is true.cos (a -b) $\neq$ cos a -cos b

Solution

Verified
Step 1
1 of 2

Take $x=y=90\text{\textdegree}$.

Then,

$\cos(x-y)=\cos (90\text{\textdegree}-90\text{\textdegree})=\cos 0\text{\textdegree}=1$

$\cos x-\cos y=\cos 90\text{\textdegree}-\cos 90\text{\textdegree}=0-0=0$

So, statement $\cos (x-y)\ne \cos x-\cos y$ is true for $x=y=90\text{\textdegree}$.

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