Trigonometry, SMB-065

Find the value of \(\theta\), correct to 1 decimal place. (2 marks)

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\(\theta=38.9^{\circ}\)

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\(\cos A\)	\(= \dfrac{b^2+c^2-a^2}{2bc} \)
\(\cos \theta\)	\(= \dfrac{9^2+5^2-6^2}{2 \times 9 \times 5}\)
	\(= 0.777…\)
\(\therefore \theta\)	\(= \cos^{-1} (0.777…) \)
	\(=38.94…^{\circ} \)
	\(=38.9^{\circ}\ \ \text{(1 d.p.)} \)