3 years ago

A cell phone company charges $40 per month plus a $35 activation fee. Write an expression for the total cost for m montha.

1 answer:

Pie3 years ago

6 0

For the first month it will be $40 for the service and $35 to activate the phone service. After the first month it will only be $40 but for the first month it will be $75

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How do I get this answer?

Keith_Richards [23]

Answer:

Step-by-step explanation:

Several trig identities are involved in the proof of this. This is the order in which they are used.

cos(2x) = cos²(x) -sin²(x)
cos²(x) +sin²(x) = 1
cos(x) = 1/sec(x)

<h3>Proof</h3>

Starting with the left side, we can transform it into the right side.

$2\cos(2x)=2(\cos^2(x)-\sin^2(x)) = 2(\cos^2(x)-(1-\cos^2(x)))\\\\=2(2\cos^2(x)-1)=2\left(\dfrac{2}{\sec^2(x)}-\dfrac{\sec^2(x)}{\sec^2(x)}\right)\\\\=\boxed{\dfrac{4-2\sec^2(x)}{\sec^2(x)}}$