12. Trigonometric Identities

Find the exact value of the expression.

$\(\cos\)105\(\degree\)$

Find the exact value of the expression.

$\(\cos\)80\(\degree\[\cos\)20\(\degree\)+\(\sin\)80\(\degree\]\sin\)20\(\degree\)$

Find the exact value of the expression.

$\(\cos\]\frac{5\pi}{12}\)$

Expand the expression using the sum & difference identities and simplify.

$\(\tan\[\left\)(-\(\theta\)-\(\frac{\pi}{2}\]\right\))$

Find the exact value of the expression.

$\(\sin\)15\(\degree\)$

Find $\(\cos\]\left\)(a+b\(\right\))$ given $\(\cos\) a=\(\frac\)12$, $\(\sin\) b=\(\frac\)12$, & $a$ is in Q IV and $b$ is in Q II.

Expand the expression using the sum & difference identities and simplify.

$\(\sin\[\left\)(-\(\theta\)-\(\frac{\pi}{2}\]\right\))$

Find the exact value of the expression.

$\(\tan\)105\(\degree\)$