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Use an Addition or Subtraction Formula to write the expression as a trigonometric function of one number.

cos(25°) cos(65°) − sin(25°) sin(65°)

 Dec 4, 2019
edited by mharrigan920  Dec 4, 2019
 #1
avatar+109399 
+1

We have that

 

cosA  cos B  - sin A sin B   =    cos (A + B)  =   cos ( 25 + 65)  =   cos (90°)   =   0

 

 

cool cool cool

 Dec 4, 2019

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