The exact value of the position of the rider after the carousel rotates 5π/12 is 5 (-√2 + √6), 5(√2 + √6).
Since the position of the carousel is (x, y) = (20cosθ, 20sinθ) and we need to find the position when θ = 5π/12 = 5π/12 × 180 = 75°
So, substituting the value of θ into the positions, we have
(20cos75°, 20sin75°)
20cos75° = 20cos(45 + 30)
Using the compound angle formula
cos(A + B) = cosAcosB - sinAsinB
With A = 45 and B = 30
cos(45 + 30) = cos45cos30 - sin45sin30
= 1/√2 × √3/2 - 1/√2 × 1/2
= 1/2√2(√3 - 1)
= 1/2√2(√3 - 1) × √2/√2
= √2(√3 - 1)/4
= (√6 - √2)/4
= (-√2 + √6)/4
So, 20cos75° = 20 × (-√2 + √6)/4
= 5 (-√2 + √6)
20sin75° = sin(45 + 30)
Using the compound angle formula
sin(A + B) = sinAcosB + cosAsinB
With A = 45 and B = 30
sin(45 + 30) = sin45cos30 + cos45sin30
= 1/√2 × √3/2 + 1/√2 × 1/2
= 1/2√2(√3 + 1)
= 1/2√2(√3 + 1) × √2/√2
= √2(√3 + 1)/4
= (√6 + √2)/4
= (√2 + √6)/4
So, 20sin75° = 20 × (√2 + √6)/4
= 5(√2 + √6)
Thus, (20cos75°, 20sin75°) = 5 (-√2 + √6), 5(√2 + √6).
So, the exact value of the position of the rider after the carousel rotates 5π/12 is 5 (-√2 + √6), 5(√2 + √6).
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