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43 votes
43 votes
What is 6cos square theta+cos theta -2=0 what the theta in degrees

User Dmitri
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1 Answer

12 votes
12 votes
Answer:
\begin{gathered} \theta=60^o \\ OR \\ \theta=131.8^o \end{gathered}

Step-by-step explanation:

Given:


6\cos^2\theta+\cos\theta-2=0

Let


\cos\theta=t

Then


\begin{gathered} 6t^2+t-2=0 \\ (2t-1)(3t+2)=0 \\ 2t-1=0 \\ \Rightarrow t=(1)/(2) \\ \\ 3t+2=0 \\ \Rightarrow t=-(2)/(3) \end{gathered}

Therefore:


\begin{gathered} \cos\theta=(1)/(2) \\ \\ \Rightarrow\theta=60^o \\ \\ \cos\theta=-(2)/(3) \\ \Rightarrow\theta=131.8^o \end{gathered}

User Mainajaved
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