SOLUTION: Please simplify each trigonometric expression: 1. cos 55� cos 25� + sin 55� sin 25� 2. sin 70� cos 10� � cos 70� sin 10�

Question 454763: Please simplify each trigonometric expression:
1. cos 55� cos 25� + sin 55� sin 25�
2. sin 70� cos 10� � cos 70� sin 10�
Answer by lwsshak3(11628) (Show Source): You can put this solution on YOUR website!
Please simplify each trigonometric expression:
1. cos 55� cos 25� + sin 55� sin 25�
2. sin 70� cos 10� � cos 70� sin 10�
..
Use following two identities to solve:
cos(s-t)=cos s cos t + sin s sin t
sin(s-t)=sin s cos t - cos s sin t
..
1. cos 55 cos 25 + sin 55 sin 25=cos(55-25)=cos(30)=√3/2
2. sin 70 cos 10 � cos 7 sin 10�=sin(70-10)=sin(60)=√3/2
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