Answer:
there are approximately 5.035 months when there is less than 9 million square meters of sea ice around the North Pole in a year.
Step-by-step explanation:
Given the data in the question;
Let S(t) represent the amount sea ice around the North Pole in millions of square meters at a given time t,
t is the number of months since January.
Now, we use a cosine curve to model this scenario
Vertical shift will be;
D = ( 6 + 14 ) / 2 = 20 / 2
D = 10
Next is the Amplitude;
|A| = ( 6 - 14 ) / 2
|A| = 4
Now, the horizontal stretch factor will be;
B = 2π / 12
B = π/6
Hence;
S(t) = 4cos( π/6 × t ) + 10 ----------- let this be equation 1
Now we find when there will be less than 9 million square meters of sea ice;
S(t) = 9
so we have
9 = 4cos( π/6 × (t-2) ) + 10
9 - 10 = 4cos( π/6 × (t-2) )
-1 = 4cos( π/6 × (t-2) )
-1/4 = cos( π/6 × (t-2) )
so we have;
cos⁻¹( -1/4 ) = π/6 × (t₁-2) -------- let this be equation 2
2π - cos⁻¹( -1/4 ) = π/6 × (t₂-2) -------- let this be equation 3
so we solve equation 2 and 3
we have'
t₁ - t₂ = 6/π × ( 2π - cos⁻¹( -1/4 ) - cos⁻¹( -1/4 ) )
t₁ - t₂ = 6/π × ( 2π - 2cos⁻¹( -1/4 )
t₁ - t₂ = 6/π × ( π - cos⁻¹( -1/4 )
t₁ - t₂ = 6/π × ( π - 104.4775 )
t₁ - t₂ = 6/π × ( π - 104.4775 )
t₁ - t₂ = 5.035
therefore, there are approximately 5.035 months when there is less than 9 million square meters of sea ice around the North Pole in a year.
