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Given that 
tan A=2 and 
sin B=(5)/(sqrt41), and that angles 
A and 
B are both in Quadrant I, find the exact value of 
sin(A-B), in simplest radical form.
Answer:

Given that tanA=2 \tan A=2 and sinB=541 \sin B=\frac{5}{\sqrt{41}} , and that angles A A and B B are both in Quadrant I, find the exact value of sin(AB) \sin (A-B) , in simplest radical form.\newlineAnswer:

Full solution

Q. Given that tanA=2 \tan A=2 and sinB=541 \sin B=\frac{5}{\sqrt{41}} , and that angles A A and B B are both in Quadrant I, find the exact value of sin(AB) \sin (A-B) , in simplest radical form.\newlineAnswer:
  1. Apply Angle Subtraction Formula: We will use the angle subtraction formula for sine, which is sin(AB)=sin(A)cos(B)cos(A)sin(B)\sin(A-B) = \sin(A)\cos(B) - \cos(A)\sin(B). To use this formula, we need to find sin(A)\sin(A), cos(A)\cos(A), and cos(B)\cos(B).
  2. Find sin(A)\sin(A), cos(A)\cos(A), cos(B)\cos(B): Since tanA=2\tan A = 2 and we are in Quadrant I, we can create a right triangle where the opposite side to angle A is 22 and the adjacent side is 11. Using the Pythagorean theorem, the hypotenuse is 12+22=5\sqrt{1^2 + 2^2} = \sqrt{5}. Therefore, sin(A)=oppositehypotenuse=25\sin(A) = \frac{\text{opposite}}{\text{hypotenuse}} = \frac{2}{\sqrt{5}}. To rationalize, we multiply by 55\frac{\sqrt{5}}{\sqrt{5}} to get sin(A)=255\sin(A) = \frac{2\sqrt{5}}{5}.
  3. Use Pythagorean Identity for sin(B)\sin(B): Using the same triangle, cos(A)=adjacenthypotenuse=15\cos(A) = \frac{\text{adjacent}}{\text{hypotenuse}} = \frac{1}{\sqrt{5}}. Rationalizing, we get cos(A)=55\cos(A) = \frac{\sqrt{5}}{5}.
  4. Calculate cos(B)\cos(B): We are given sinB=541\sin B = \frac{5}{\sqrt{41}}. To find cos(B)\cos(B), we use the Pythagorean identity sin2(B)+cos2(B)=1\sin^2(B) + \cos^2(B) = 1. Substituting sinB\sin B, we get (541)2+cos2(B)=1\left(\frac{5}{\sqrt{41}}\right)^2 + \cos^2(B) = 1. Simplifying, we get 2541+cos2(B)=1\frac{25}{41} + \cos^2(B) = 1.
  5. Substitute into Angle Subtraction Formula: Subtract 2541\frac{25}{41} from both sides to solve for cos2(B)\cos^2(B): cos2(B)=12541\cos^2(B) = 1 - \frac{25}{41}. This simplifies to cos2(B)=(4141)(2541)=1641\cos^2(B) = \left(\frac{41}{41}\right) - \left(\frac{25}{41}\right) = \frac{16}{41}. Taking the square root, cos(B)=1641=441\cos(B) = \sqrt{\frac{16}{41}} = \frac{4}{\sqrt{41}}. Since B is in Quadrant I, cos(B)\cos(B) is positive, so cos(B)=441\cos(B) = \frac{4}{\sqrt{41}}. Rationalizing, we get cos(B)=44141\cos(B) = \frac{4\sqrt{41}}{41}.
  6. Combine Terms: Now we have sin(A)=255\sin(A) = \frac{2\sqrt{5}}{5}, cos(A)=55\cos(A) = \frac{\sqrt{5}}{5}, and cos(B)=44141\cos(B) = \frac{4\sqrt{41}}{41}. We can substitute these into the angle subtraction formula: sin(AB)=(255)(44141)(55)(541)\sin(A-B) = \left(\frac{2\sqrt{5}}{5}\right)\left(\frac{4\sqrt{41}}{41}\right) - \left(\frac{\sqrt{5}}{5}\right)\left(\frac{5}{\sqrt{41}}\right).
  7. Rewrite Fraction: Multiplying the terms, we get sin(AB)=82052055541\sin(A-B) = \frac{8\sqrt{205}}{205} - \frac{5\sqrt{5}}{41}. To combine these terms, we need a common denominator, which is 205205.
  8. Subtract Fractions: We rewrite (55/41)(5\sqrt{5}/41) as (255/205)(25\sqrt{5}/205) to have the same denominator. Now, sin(AB)=(8205/205)(255/205)\sin(A-B) = (8\sqrt{205}/205) - (25\sqrt{5}/205).
  9. Final Result: Subtracting the fractions, we get sin(AB)=8205255205\sin(A-B) = \frac{8\sqrt{205} - 25\sqrt{5}}{205}. This is the exact value of sin(AB)\sin(A-B) in simplest radical form.

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