Geometry
Sum and Difference Trigonometric Formulas
Using the cosine difference formula, what is the value of
\[ \cos 15 ^ \circ ?\]
Which of the following is equal to
\[ \cos 56 ^ \circ \cos 11 ^ \circ + \sin 56 ^ \circ \sin 11 ^ \circ ? \]
Which of the following is equal to
\[ \cos 15 ^ \circ \cos 45 ^ \circ - \sin 15 ^ \circ \sin 45 ^ \circ ?\]
Which of the following is NOT equal to \( \cos 2 \theta \)?
\(N\) and \(M\) are real numbers such that
\[ \cos ( \alpha + \beta) = N \cos \alpha \cos \beta + M \sin \alpha \sin \beta \]
is an algebraic identity. What is the value of \(N+M\).