gaokao 2020 Q7

gaokao · China · national-III-science 5 marks Sine and Cosine Rules Find an angle using the cosine rule
In $\triangle A B C$ , $\cos C = \frac { 2 } { 3 } , A C = 4 , B C = 3$ , then $\cos B =$
A. $\frac { 1 } { 9 }$
B. $\frac { 1 } { 3 }$
C. $\frac { 1 } { 2 }$
D. $\frac { 2 } { 3 }$
In $\triangle A B C$ , $\cos C = \frac { 2 } { 3 } , A C = 4 , B C = 3$ , then $\cos B =$

A. $\frac { 1 } { 9 }$

B. $\frac { 1 } { 3 }$

C. $\frac { 1 } { 2 }$

D. $\frac { 2 } { 3 }$