Answer:
[tex]cos(\frac{t}{2} ) = -\sqrt\frac{1}{11}[/tex]
Step-by-step explanation:
The relationship between cos(t) and cos([tex]\frac{t}{2}[/tex]) is:
[tex]cos(\frac{t}{2} ) = a\sqrt\frac{1+cos(t)}{2}[/tex]
where a is equal to +1 or -1 is same as same sign which cos(t) holds.
Thus, [tex]cos(\frac{t}{2} ) = -\sqrt\frac{1-\frac{9}{11}}{2}[/tex]
⇒ [tex]cos(\frac{t}{2} ) = -\sqrt\frac{11-9}{2\times 11}[/tex]
⇒ [tex]cos(\frac{t}{2} ) = -\sqrt\frac{2}{22}[/tex]
⇒ [tex]cos(\frac{t}{2} ) = -\sqrt\frac{1}{11}[/tex]
