gaokao 2020 Q9

gaokao · China · national-I-science 5 marks Trig Proofs Trigonometric Equation Constraint Deduction
Given $\alpha \in ( 0 , \pi )$ and $3 \cos 2 \alpha - 8 \cos \alpha = 5$, then $\sin \alpha =$
A. $\frac { \sqrt { 5 } } { 3 }$
B. $\frac { 2 } { 3 }$
C. $\frac { 1 } { 3 }$
D. $\frac { \sqrt { 5 } } { 9 }$ 
Given $\alpha \in ( 0 , \pi )$ and $3 \cos 2 \alpha - 8 \cos \alpha = 5$, then $\sin \alpha =$\\
A. $\frac { \sqrt { 5 } } { 3 }$\\
B. $\frac { 2 } { 3 }$\\
C. $\frac { 1 } { 3 }$\\
D. $\frac { \sqrt { 5 } } { 9 }$
Paper Questions
Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 Q9