Ifcos 6theta + cos 4theta + cos 2theta + 1 = | vedclass

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Question

(d) $\cos 6	heta + \cos 4	heta + \cos 2	heta + 1 = 0$  

$ \Rightarrow $$2{\cos ^2}3	heta + 2\cos 3	heta \,.\,\cos 	heta = 0$

$ \Right

Vedclass · Accepted Answer

${30^o},{45^o},{90^o},{135^o},{150^o}$

Vedclass · Answer

(d) $\cos 6	heta + \cos 4	heta + \cos 2	heta + 1 = 0$  

$ \Rightarrow $$2{\cos ^2}3	heta + 2\cos 3	heta \,.\,\cos 	heta = 0$

$ \Rightarrow $ $4\cos 3	heta \cos 2	heta \cos 	heta = 0$ 

$ \Rightarrow $ $3	heta = (2n + 1)\frac{\pi }{2};\,\,2	heta = (2n + 1)\frac{\pi }{2}{m{\, and\,\, }}	heta = (2n + 1)\frac{\pi }{2}$ 

$ \Rightarrow $ $	heta = {30^o},\,{90^o},\,{150^o},\,{45^o},\,{135^o}$.

If$\cos 6\theta + \cos 4\theta + \cos 2\theta + 1 = 0$, where $0 < \theta < {180^o}$, then $\theta =$

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