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Express 4 cos θ – 3 sin θ in the form R sin(θ – α), where R > 0 and 0° < α < 360°, giving α to the nearest degree. Solve the equation 4 cos θ – 3 sin θ = 3, for 0° ≤ θ ≤ 360°.
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2 partsStep-by-step solution
8 stepsPart a· 3 steps
We want to express in the form .
First, expand using the compound angle formula:
Rearrange the given expression to match the terms:
Comparing coefficients:
Find .
Square equations (1) and (2) and add them:
Since ,
Find .
Divide equation (2) by equation (1):
Since (negative) and (negative), must be in the third quadrant.
The reference angle is .
Therefore, .
Rounding to the nearest degree, .Write the expression in the required form.
The final answer is .
Part b
We need to solve the equation for .
From part (a), we know that .
So, the equation becomes:
Isolate the sine term.
Let .
Determine the range for .
Given :Find the principal value for .
This value is within the range .
Find other possible values for within the range.
Since is positive, can be in the first or second quadrant.
The second general solution is .This value is not within the range as .
We also need to consider solutions by subtracting .
For : . This is not within the range as .
For : . This value is within the range .So, the valid values for are approximately and .
Solve for using .
For :
For :
Rounding to one decimal place:
The final answers are .
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