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Ch. 7 - Logarithmic, Exponential Functions, and Hyperbolic Functions
Briggs - Calculus: Early Transcendentals 3rd Edition
Briggs3rd EditionCalculus: Early TranscendentalsISBN: 9780136847243Non è quello che usi tu?Cambia libro di testo
Tutti i libri di testoBriggs 3rd EditionCh. 7 - Logarithmic, Exponential Functions, and Hyperbolic FunctionsProblema 7.2.24c
Capitolo 7, Problema 7.2.24c

Energy consumption On the first day of the year (t=0), a city uses electricity at a rate of 2000 MW. That rate is projected to increase at a rate of 1.3% per year.


c. Find a function that gives the total energy used (in MW-yr) between t=0 and any future time t>0.

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Identify the given information: the initial rate of electricity consumption at time \(t=0\) is 2000 MW, and the rate increases by 1.3% per year. This suggests the rate function grows exponentially.
Express the rate of electricity consumption as a function of time \(t\). Since the rate increases by 1.3% per year, the rate function can be written as \(R(t) = 2000 \times (1.013)^t\), where \(t\) is in years.
Understand that the total energy used between \(t=0\) and any future time \(t\) is the integral of the rate function over that interval. So, the total energy function \(E(t)\) is given by the integral \(E(t) = \int_0^t R(x) \, dx\).
Set up the integral explicitly: \(E(t) = \int_0^t 2000 \times (1.013)^x \, dx\). This integral will give the total energy consumed in megawatt-years (MW-yr) from time 0 to time \(t\).
To solve the integral, recall that the integral of an exponential function \(a^x\) with respect to \(x\) is \(\frac{a^x}{\ln(a)}\). Use this formula to express \(E(t)\) in terms of \(t\) without calculating the final numeric value.

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Exponential Growth

Exponential growth describes a process where a quantity increases at a rate proportional to its current value. In this problem, the electricity usage rate grows by 1.3% per year, meaning the rate function can be modeled as an exponential function of time.
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Exponential Growth & Decay

Integration of a Rate Function

To find the total quantity accumulated over time from a rate function, we integrate the rate with respect to time. Here, integrating the power consumption rate over the interval [0, t] gives the total energy used in megawatt-years.
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Intro To Related Rates

Units and Interpretation of the Integral

Understanding units is crucial: the rate is in megawatts (MW), and integrating over time (years) yields energy in megawatt-years (MW-yr). This helps interpret the integral as total energy consumed, not just instantaneous power.
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Evaluate Composite Functions - Values on Unit Circle
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