Cos(phi+tetha)+cos(phi-tetha)=

By Admin ReiPosted on October 28, 2022

A. Cos tetha
B. Sin tetha
C. 2 cos tetha
D.-2cos tetha
E.-cos 2 tetha

Cos(phi+tetha)+cos(phi-tetha)=

Cos (phi + teta) + cos (phi – teta)
= – cos (teta) – cos (teta)
= -2cos(teta)

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