Find tan θ if cos θ = 1/4 and sin θ < 0.
1 answer:
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The cosine of an angle is the x-coordinate of the point where its terminal ray intersects the unit circle. So, we can draw a line at x=-1/2 and see where it intersects the unit circle. That will tell us possible values of θ/2.
We find that vertical line intersects the unit circle at points where the rays make an angle of ±120° with the positive x-axis. If you consider only positive angles, these angles are 120° = 2π/3 radians, or 240° = 4π/3 radians. Since these are values of θ/2, the corresponding values of θ are double these values.
a) The cosine values repeat every 2π, so the general form of the smallest angle will be
... θ = 2(2π/3 + 2kπ) = 4π/3 + 4kπ
b) Similarly, the values repeat for the larger angle every 2π, so the general form of that is
... θ = 2(4π/3 + 2kπ) = 8π/3 + 4kπ
c) Using these expressions with k=0, 1, 2, we get
... θ = {4π/3, 8π/3, 16π/3, 20π/3, 28π/3, 32π/3}
Answer:
See attached image for the drawing of the first four trees (circled in green)
The patterns is:
x = 2+3n and y= 3+2n
Position of 7th tree is: (20,15) (circled in orange in the image)
Step-by-step explanation:
Starting at the location (2,3) the next x and y positions are given by:
x = 2+3n since the horizontal position needs to be increased by 3 units on each iteration,
and y= 3+2n since the vertical position needs to be increased by 2 units on each iteration
being n= 1 through 6 (to account for the next 6 trees that need to be planted)
With such pattern, the location of the seventh tree would be:
x = 2 + 3*6 =2 + 18 = 20
y = 3 + 2*6 = 3 + 12 = 15
That is, the point (20,15) on the plane.
Also see attached image.
