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A weight is attached to a spring that is fixed to the floor. The equation h=7cos (π3t)
models the height, h, in centimeters after t seconds of the weight being stretched and released.

a. Solve the equation for t.

b. Find the times at which the weight is first at a height of 1 cm, of 3 cm, and of 5 cm above the rest position. Calculate your answer using radian angle measure. Round your answers to the nearest hundredth.

1 answer

a. To solve the equation for t, we need to isolate t. The equation is h = 7cos(π/3 * t). To isolate t, we divide both sides by 7 first:

h/7 = cos(π/3 * t)

Next, we take the inverse cosine of both sides to solve for t:

cos^(-1)(h/7) = π/3 * t

Multiply both sides by 3/π to solve for t:

t = 3π * cos^(-1)(h/7)

b. To find the times at which the weight is first at a height of 1 cm, 3 cm, and 5 cm above the rest position, we substitute these heights into the equation and solve for t:

For h = 1 cm:
t = 3π * cos^(-1)(1/7) ≈ 0.53 seconds

For h = 3 cm:
t = 3π * cos^(-1)(3/7) ≈ 1.74 seconds

For h = 5 cm:
t = 3π * cos^(-1)(5/7) ≈ 2.54 seconds

Therefore, the times at which the weight is first at a height of 1 cm, 3 cm, and 5 cm above the rest position are approximately 0.53 seconds, 1.74 seconds, and 2.54 seconds, respectively.