Use sum-to-product formulas to rewrite the expression as a product.cos 5x + cos 3x
A. 2 cos 4x sin x
B. 2 sin 4x sin x
C. 2 cos 4x cos x
D. 2 cos 4x
Answer: C
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Use the graph of the piecewise function f(x) to find the following.(f ? f)(-3)
A. 1 B. 3 C. 0 D. 2
Solve.For a resistor in a direct current circuit that does not vary its resistance, the power that a resistor must dissipate is directly proportional to the square of the voltage across the resistor. The resistor must dissipate 
watt of power when the voltage across the resistor is 7 volts. Find the power that the resistor must dissipate when the voltage across it is 21 volts.
A. 
watt
B. 
watt
C. 
watt
D. 
watts
Identify the quadrant with the given condition.The first and second coordinates have the opposite signs.
A. I and IV B. II and III C. II and IV D. I and III
Use the graph to find the indicated function value.y = f(x). Find f(2)
A. 0.4 B. -4.5 C. 4.5 D. -0.4