# trig

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using the trigonometric identities find the exact (radical form) value of cos (105 degrees)

• trig -

cos 105°
= cos(60+45)
= cos60cos45 - sin60sin45
= (1/2)(√2/2) - (√3/2)(√2/2)
= (√2 - √6)/4

• trig -

cos195

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