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Given that 
tan x=sqrt3 and 
tan y=(3)/(sqrt7), and that angles 
x and 
y are both in Quadrant I, find the exact value of 
sin(x-y), in simplest radical form.
Answer:

Given that tanx=3 \tan x=\sqrt{3} and tany=37 \tan y=\frac{3}{\sqrt{7}} , and that angles x x and y y are both in Quadrant I, find the exact value of sin(xy) \sin (x-y) , in simplest radical form.\newlineAnswer:

Full solution

Q. Given that tanx=3 \tan x=\sqrt{3} and tany=37 \tan y=\frac{3}{\sqrt{7}} , and that angles x x and y y are both in Quadrant I, find the exact value of sin(xy) \sin (x-y) , in simplest radical form.\newlineAnswer:
  1. Use Angle Subtraction Formula: We will use the angle subtraction formula for sine, which is sin(xy)=sin(x)cos(y)cos(x)sin(y)\sin(x-y) = \sin(x)\cos(y) - \cos(x)\sin(y). To find sin(x)\sin(x) and cos(x)\cos(x), we use the fact that tanx=sinxcosx\tan x = \frac{\sin x}{\cos x}. Since tanx=3\tan x = \sqrt{3}, we can create a right triangle where the opposite side to angle xx is 3\sqrt{3} and the adjacent side is 11, because tanx=oppositeadjacent\tan x = \frac{\text{opposite}}{\text{adjacent}}. Then, using the Pythagorean theorem, we find the hypotenuse.
  2. Find Triangle Sides: For angle xx, we have tanx=31\tan x = \frac{\sqrt{3}}{1}, so the sides of the triangle are opposite = 3\sqrt{3}, adjacent = 11. Using the Pythagorean theorem, hypotenuse2=opposite2+adjacent2\text{hypotenuse}^2 = \text{opposite}^2 + \text{adjacent}^2, we get hypotenuse2=(3)2+12=3+1=4\text{hypotenuse}^2 = (\sqrt{3})^2 + 1^2 = 3 + 1 = 4. Therefore, the hypotenuse is 4=2\sqrt{4} = 2.
  3. Calculate sinx\sin x and cosx\cos x: Now we can find sinx\sin x and cosx\cos x. Since sinx=oppositehypotenuse\sin x = \frac{\text{opposite}}{\text{hypotenuse}}, we have sinx=32\sin x = \frac{\sqrt{3}}{2}. And since cosx=adjacenthypotenuse\cos x = \frac{\text{adjacent}}{\text{hypotenuse}}, we have cosx=12\cos x = \frac{1}{2}.
  4. Find Triangle Sides: Next, we find siny\sin y and cosy\cos y using the same method. We have tany=37\tan y = \frac{3}{\sqrt{7}}, so we can create a right triangle where the opposite side to angle yy is 33 and the adjacent side is 7\sqrt{7}. Again, using the Pythagorean theorem, we find the hypotenuse.
  5. Calculate siny\sin y and cosy\cos y: For angle yy, we have tany=37\tan y = \frac{3}{\sqrt{7}}, so the sides of the triangle are opposite = 33, adjacent = 7\sqrt{7}. Using the Pythagorean theorem, hypotenuse2=opposite2+adjacent2\text{hypotenuse}^2 = \text{opposite}^2 + \text{adjacent}^2, we get hypotenuse2=32+(7)2=9+7=16\text{hypotenuse}^2 = 3^2 + (\sqrt{7})^2 = 9 + 7 = 16. Therefore, the hypotenuse is 16=4\sqrt{16} = 4.
  6. Substitute Values: Now we can find siny\sin y and cosy\cos y. Since siny=oppositehypotenuse\sin y = \frac{\text{opposite}}{\text{hypotenuse}}, we have siny=34\sin y = \frac{3}{4}. And since cosy=adjacenthypotenuse\cos y = \frac{\text{adjacent}}{\text{hypotenuse}}, we have cosy=74\cos y = \frac{\sqrt{7}}{4}.
  7. Simplify Expression: We can now substitute the values of sinx\sin x, cosx\cos x, siny\sin y, and cosy\cos y into the angle subtraction formula for sine: sin(xy)=sin(x)cos(y)cos(x)sin(y)=(3/2)(7/4)(1/2)(3/4)\sin(x-y) = \sin(x)\cos(y) - \cos(x)\sin(y) = (\sqrt{3}/2)(\sqrt{7}/4) - (1/2)(3/4).
  8. Combine Terms: Simplify the expression: sin(xy)=37241324=21838.\sin(x-y) = \frac{\sqrt{3} \cdot \sqrt{7}}{2 \cdot 4} - \frac{1 \cdot 3}{2 \cdot 4} = \frac{\sqrt{21}}{8} - \frac{3}{8}.
  9. Combine Terms: Simplify the expression: sin(xy)=(3×7)/(2×4)(1×3)/(2×4)=(21/8)(3/8)\sin(x-y) = (\sqrt{3} \times \sqrt{7})/(2 \times 4) - (1 \times 3)/(2 \times 4) = (\sqrt{21}/8) - (3/8).Combine the terms to get the final answer: sin(xy)=(213)/8\sin(x-y) = (\sqrt{21} - 3)/8.

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