If \(
\cos x = -\frac{1}{2},
\) x lies in third quadrant, then tanx = ?
Using cos(A + B) = cosA cosB - sinA sinB, find the value of cos75°.
\(
\frac{\sqrt{5} - 1}{4}
\)
\(
\frac{\sqrt{5} + 1}{4}
\)
\(
\frac{\sqrt{6} - \sqrt{2}}{4}
\)
\(
\frac{\sqrt{6} + \sqrt{2}}{4}
\)