SAT Math Practice Question #23419 - SATify | SATify

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SAT Math Practice Question #23419 - SATify | SATify

#23419

trigonometry

algebra

Calculus

hard

150 sec

Suppose that $sin a + sin b = \frac{5}{3}$ and $cos a + cos b = 1$ . What is $cos (a + b)$ ?

A.

$- \frac{1}{2}$

B.

$- \frac{1}{4}$

C.

$0$

D.

$\frac{1}{4}$

E.

$\frac{1}{2}$