AP EAMCET · Maths · Trigonometric Equations
If \(\sin A+\sin B+\sin C=0\) and \(\cos A+\cos B+\cos C=0\), then \(\cos (A+B)+\cos (B+C)+\cos (C+A)\) is equal to
- A \(\cos (A+B+C)\)
- B \(2\)
- C \(1\)
- D \(0\)
Answer & Solution
Correct Answer
(D) \(0\)
Step-by-step Solution
Detailed explanation
Here, we have the pattern of data in \(\cos x\) and \(\sin x\), so let's use the method of polar form of complex number. Polar form of complex number, \(z=\cos \theta+i \sin \theta\) then \(\bar{z}=\cos \theta-i \sin \theta\) and \(z \bar{z}=1\)…
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