What is the definition of the cosine function in relation to a right triangle using the adjacent side and hypotenuse?

Find all solutions of the equation \( 2 \cos x-1=0 \). The answer is \( A+B k \pi \) and \( C+D k \pi \) where \( k \) is any integer, \( 0<A<C<2 \pi \), \( A=\square, D=\square \) \( C=\square \)

\( \frac { 4 \sin \frac { \alpha } { 2 } \cos \frac { \alpha } { 2 } } { \tan \frac { \alpha } { 2 } } - 1 \)

If \( \theta=\frac{5 \pi}{6} \), then \( \cos (\theta)=\square \) \( \sin (\theta)=\square \) Give exact values. No decimals allowed!

Solve \( 8 \sin (6 x)=7 \) for the two smallest positive solutions \( A \) and \( B \), with \( A<B \) \( A=\square \) \( B=\square \) Give your answers accurate to at least two decimal places.

Which is the correct identity for cos? \( \cos \theta=\frac{h}{a} \) \( \cos =\frac{h}{a} \) \( \cos \theta=\frac{a}{h} \) \( \cos =\frac{a}{h} \)