Find the exact value of cos 8*cos 38 + sin 8* sin 38

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justaguide | College Teacher | (Level 2) Distinguished Educator

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The value of cos 8*cos 38 + sin 8* sin 38 has to be determined. Use the relation cos x*cos y + sin x*sin y = cos(x - y)

cos 8*cos 38 + sin 8* sin 38

=> cos (38 - 8)

=> cos 30

=> `sqrt 3/2`

The value of cos 8*cos 38 + sin 8* sin 38 is `sqrt 3/2`

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