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If cos alpha=4/5 and cos beta =5/13, pro...

If `cos alpha=4/5 and cos beta =5/13,` prove that `cos (alpha-beta)=56/65`

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Given, `cosalpha=4/5​`
`=>sinalpha=sqrt(1-cos^2alpha)`
​`=> sinalpha=sqrt(1-(16)/(25))`
​`=> ​ sinalpha=sqrt((9)/(25))`
​`=> sinalpha=3/5`
and `cosbeta=5/13​`
...
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