Aim for FivePrecalculus

Symbolic manipulations

A log quotient, arctangent and a double angle

  • Units 2 and 3
  • 6 points
  • About 18 minutes

You solve exponential, logarithmic and trigonometric equations by hand and rewrite log, exponential and trig expressions in equivalent forms, giving exact answers and showing your work. No calculator. On the exam: Question 4 of 4. Part B of the free-response section: 2 questions in 35 minutes, no calculator allowed.

The question

No calculator is allowed for this question. Angle measures are in radians. Unless otherwise specified, the domain of a function f is the set of all real numbers x for which f(x) is a real number, and solutions to equations must be real numbers. Give the exact value of any expression that can be evaluated without a calculator (for example, log₂ 8, cos(π/2) and arcsin(1)). Unless otherwise specified, combine terms using algebra and the rules for exponents and logarithms (for example, write x²·x³ as x⁵, and ln 3 + ln 5 as ln 15). Show the work that leads to each answer.

Suggested time: 18 minutes

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Part (a)

2 points

The functions g and h are given by g(x) = log₂(x + 3) − log₂(x − 1) and h(x) = 2 arctan x. (i) Solve g(x) = 2 for values of x in the domain of g. (ii) Solve h(x) = −π/2 for values of x in the domain of h.

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Part (b)

2 points

The functions j and k are given by j(x) = 27ˣ · 3^(2 − x) and k(x) = cos(x − π/4) + cos(x + π/4). (i) Rewrite j(x) in the form a · bˣ, where a and b are constants. (ii) Rewrite k(x) as a single term of the form A cos x, where A is a constant.

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Part (c)

2 points

Find all values of x in the interval [0, 2π) for which sin(2x) = cos x.

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