Answer:
[tex]\cos(\frac{1}{2}A) = {\frac{\sqrt{3}}{2}[/tex]
Step-by-step explanation:
Given
[tex]\cos A = \frac{1}{2}[/tex]
Required
Determine [tex]\cos(\frac{1}{2}A)[/tex]
To do this, we make use of the following identity
[tex]\cos(\frac{1}{2}A) = \sqrt{\frac{\cos A+1}{2}}[/tex]
Substitute: [tex]\cos A = \frac{1}{2}[/tex]
[tex]\cos(\frac{1}{2}A) = \sqrt{\frac{\frac{1}{2}+1}{2}}[/tex]
Solve the numerator
[tex]\cos(\frac{1}{2}A) = \sqrt{\frac{\frac{2+1}{2}}{2}}[/tex]
[tex]\cos(\frac{1}{2}A) = \sqrt{\frac{\frac{3}{2}}{2}}[/tex]
Rewrite as:
[tex]\cos(\frac{1}{2}A) = \sqrt{\frac{3}{2} * \frac{1}{2}}[/tex]
[tex]\cos(\frac{1}{2}A) = \sqrt{\frac{3}{4}}[/tex]
Take square roots
[tex]\cos(\frac{1}{2}A) = {\frac{\sqrt{3}}{2}[/tex]
