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Question
Evaluate the following
cos 60° cos 45° - sin 60° ∙ sin 45°
Solution
cos 60° cos 45° - sin 60° ∙ sin 45° …(i)
By trigonometric ratios we know that,
`cos 60^@ = 1/2 cos 45^@ = 1/sqrt2`
`sin 60^@ = sqrt3/2 sin 45^@ = 1/sqrt2`
By substituting above value in (i), we get
`1/2. 1/sqrt2 - sqrt3/2. 1/sqrt2 => (1 - sqrt3)/(2sqrt2)`
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