Which expression is equivalent to cos(103°)cos(54°) – sin(103°)sin(54°)?
Answer
A
sin(49°)
B
cos(49°)
C
sin(157°)
D
cos(157°)
Explanation
Use the cosine addition identity: cos(A + B) = cos(A)cos(B) − sin(A)sin(B). With A = 103° and B = 54°, the expression equals cos(103° + 54°) = cos(157°), which is choice D.
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