csat-suneung 2014 Q3

csat-suneung · South-Korea · csat__math-B 2 marks Addition & Double Angle Formulae Direct Double Angle Evaluation
When $\tan \theta = \frac { \sqrt { 5 } } { 5 }$, what is the value of $\cos 2 \theta$? [2 points]
(1) $\frac { \sqrt { 2 } } { 3 }$
(2) $\frac { \sqrt { 3 } } { 3 }$
(3) $\frac { 2 } { 3 }$
(4) $\frac { \sqrt { 5 } } { 3 }$
(5) $\frac { \sqrt { 6 } } { 3 }$
When $\tan \theta = \frac { \sqrt { 5 } } { 5 }$, what is the value of $\cos 2 \theta$? [2 points]\\
(1) $\frac { \sqrt { 2 } } { 3 }$\\
(2) $\frac { \sqrt { 3 } } { 3 }$\\
(3) $\frac { 2 } { 3 }$\\
(4) $\frac { \sqrt { 5 } } { 3 }$\\
(5) $\frac { \sqrt { 6 } } { 3 }$