Q. Given that tanx=3 and tany=73, and that angles x and y are both in Quadrant I, find the exact value of sin(x−y), in simplest radical form.Answer:
Use Angle Subtraction Formula: We will use the angle subtraction formula for sine, which is sin(x−y)=sin(x)cos(y)−cos(x)sin(y). To find sin(x) and cos(x), we use the fact that tanx=cosxsinx. Since tanx=3, we can create a right triangle where the opposite side to angle x is 3 and the adjacent side is 1, because tanx=adjacentopposite. Then, using the Pythagorean theorem, we find the hypotenuse.
Find Triangle Sides: For angle x, we have tanx=13, so the sides of the triangle are opposite = 3, adjacent = 1. Using the Pythagorean theorem, hypotenuse2=opposite2+adjacent2, we get hypotenuse2=(3)2+12=3+1=4. Therefore, the hypotenuse is 4=2.
Calculate sinx and cosx: Now we can find sinx and cosx. Since sinx=hypotenuseopposite, we have sinx=23. And since cosx=hypotenuseadjacent, we have cosx=21.
Find Triangle Sides: Next, we find siny and cosy using the same method. We have tany=73, so we can create a right triangle where the opposite side to angle y is 3 and the adjacent side is 7. Again, using the Pythagorean theorem, we find the hypotenuse.
Calculate siny and cosy: For angle y, we have tany=73, so the sides of the triangle are opposite = 3, adjacent = 7. Using the Pythagorean theorem, hypotenuse2=opposite2+adjacent2, we get hypotenuse2=32+(7)2=9+7=16. Therefore, the hypotenuse is 16=4.
Substitute Values: Now we can find siny and cosy. Since siny=hypotenuseopposite, we have siny=43. And since cosy=hypotenuseadjacent, we have cosy=47.
Simplify Expression: We can now substitute the values of sinx, cosx, siny, and cosy into the angle subtraction formula for sine: sin(x−y)=sin(x)cos(y)−cos(x)sin(y)=(3/2)(7/4)−(1/2)(3/4).
Combine Terms: Simplify the expression: sin(x−y)=2⋅43⋅7−2⋅41⋅3=821−83.
Combine Terms: Simplify the expression: sin(x−y)=(3×7)/(2×4)−(1×3)/(2×4)=(21/8)−(3/8).Combine the terms to get the final answer: sin(x−y)=(21−3)/8.
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