Find the maximum value of 3cos θ + 4sin θ + 5cos(θ + π/6).

Answer: The maximum value of the expression is 30+153\sqrt{30 + 15\sqrt{3}}.

Step-by-step solution

Step 1: Expand the expression

First, we expand the term 5cos⁡(θ+π/6)5\cos(\theta + \pi/6) using the trigonometric identity cos⁡(A+B)=cos⁡Acos⁡B−sin⁡Asin⁡B\cos(A+B) = \cos A \cos B - \sin A \sin B. This will allow us to combine like terms involving cos⁡θ\cos \theta and sin⁡θ\sin \theta.

Step 2: Substitute known values and simplify

We substitute the known values for cos⁡(π/6)=3/2\cos(\pi/6) = \sqrt{3}/2 and sin⁡(π/6)=1/2\sin(\pi/6) = 1/2. Then, we group the coefficients of cos⁡θ\cos \theta and sin⁡θ\sin \theta to simplify the expression into the form Acos⁡θ+Bsin⁡θA\cos \theta + B\sin \theta.

Step 3: Apply the maximum value formula

For an expression of the form Acos⁡θ+Bsin⁡θA\cos \theta + B\sin \theta, its maximum value is given by A2+B2\sqrt{A^2 + B^2}. Here, A=6+532A = \frac{6+5\sqrt{3}}{2} and B=32B = \frac{3}{2}.

Step 4: Calculate A2A^2

We calculate the square of AA. Remember to square both the numerator and the denominator, and use the formula (a+b)2=a2+2ab+b2(a+b)^2 = a^2 + 2ab + b^2 for the numerator.

Step 5: Calculate B2B^2 and A2+B2A^2 + B^2

Next, we calculate the square of BB. Then, we add A2A^2 and B2B^2 together. Since they have a common denominator, we can simply add the numerators.

Step 6: Find the maximum value

Finally, we take the square root of the sum A2+B2A^2 + B^2 to find the maximum value of the given expression.

More from this chapter

All Trigonometric Functions solutions →

Solve your own maths question free →