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Question 8
Solve, for $0 heta < 360^ ext{o}$, the equation 9sin(θ + 60°) = 4 giving your answers to 1 decimal place. You must show each step of your working. Solve, for $- e... show full transcript
Step 1
Answer
To solve the equation, we start with:
Dividing both sides by 9: ext{sin}( heta + 60^ ext{o}) = rac{4}{9}
Next, we find the angle whose sine is rac{4}{9}:
heta + 60^ ext{o} = ext{sin}^{-1}igg(rac{4}{9}igg)\ heta + 60^ ext{o} ext{ is approximately } 26.3877^ ext{o}
To find other angles within the range, we can also use: heta + 60^ ext{o} = 180^ ext{o} - ext{sin}^{-1}igg(rac{4}{9}igg)\ heta + 60^ ext{o} = 180^ ext{o} - 26.3877^ ext{o}
Calculating this gives:
Subtracting 60° from both results:
ightarrow heta ext{ is approximately } -33.6123^ ext{o} ext{ (not within range)} heta = 153.6123^ ext{o} - 60^ ext{o} ightarrow heta ext{ is approximately } 93.6123^ ext{o}$$
Now continuing with the other case: Subtracting 60° again:
ightarrow heta ext{ is approximately } 273.6123^ ext{o} \ heta = 273.6^ ext{o} \ ext{(not within } 0 < heta < 360)$$ Thus, the answers in the correct range are: $$ heta ext{ approximately } 93.6^ ext{o} ext{ and } 326.4^ ext{o}$$Step 2
Answer
Starting with the equation:
This can be rearranged as:
Recalling that ext{tan}x = rac{ ext{sin}x}{ ext{cos}x}, we substitute: 2 rac{ ext{sin}x}{ ext{cos}x} = 3 ext{sin}x
Dividing both sides by (assuming ): rac{2}{ ext{cos}x} = 3
This simplifies to: ext{cos}x = rac{2}{3}
Now taking the inverse cosine: x = ext{cos}^{-1}igg(rac{2}{3}igg)\ x ext{ is approximately } 0.8411
The second solution in the range can be found using: x = - ext{cos}^{-1}igg(rac{2}{3}igg)\ x ext{ is approximately } -0.8411
Thus the solutions are:
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