Choose the one alternative that best completes the statement or answers the question.
Find the exact value of the expression. Do not use a calculator.
-$\cos 35 ^ { \circ } \sin 55 ^ { \circ } + \sin 35 ^ { \circ } \cos 55 ^ { \circ }$
A) $- 1$
B) 2
C) 0
D) 1

Question

Quizplus · Accepted Answer

This expression is an application of the sine addition formula, $\sin(a + b) = \sin a \cos b + \cos a \sin b$. Here, $a = 35^\circ$ and $b = 55^\circ$, so the expression simplifies to $\sin(35^\circ + 55^\circ) = \sin(90^\circ)$, which equals 1.

Choose the One Alternative That Best Completes the Statement or Answers