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If 
cos A=(21)/(29) and 
tan B=(5)/(12) and angles A and B are in Quadrant I, find the value of 
tan(A+B).
Answer:

If cosA=2129 \cos A=\frac{21}{29} and tanB=512 \tan B=\frac{5}{12} and angles A and B are in Quadrant I, find the value of tan(A+B) \tan (A+B) .\newlineAnswer:

Full solution

Q. If cosA=2129 \cos A=\frac{21}{29} and tanB=512 \tan B=\frac{5}{12} and angles A and B are in Quadrant I, find the value of tan(A+B) \tan (A+B) .\newlineAnswer:
  1. Find tanA\tan A: Use the identity for the tangent of the sum of two angles: tan(A+B)=tanA+tanB1tanAtanB\tan(A+B) = \frac{\tan A + \tan B}{1 - \tan A \cdot \tan B}. First, we need to find tanA\tan A. Since we know cosA=2129\cos A = \frac{21}{29} and AA is in Quadrant I, we can find sinA\sin A using the Pythagorean identity sin2A+cos2A=1\sin^2 A + \cos^2 A = 1. sin2A=1cos2A\sin^2 A = 1 - \cos^2 A sin2A=1(2129)2\sin^2 A = 1 - \left(\frac{21}{29}\right)^2 sin2A=1441841\sin^2 A = 1 - \frac{441}{841} tan(A+B)=tanA+tanB1tanAtanB\tan(A+B) = \frac{\tan A + \tan B}{1 - \tan A \cdot \tan B}00 tan(A+B)=tanA+tanB1tanAtanB\tan(A+B) = \frac{\tan A + \tan B}{1 - \tan A \cdot \tan B}11 tan(A+B)=tanA+tanB1tanAtanB\tan(A+B) = \frac{\tan A + \tan B}{1 - \tan A \cdot \tan B}22 tan(A+B)=tanA+tanB1tanAtanB\tan(A+B) = \frac{\tan A + \tan B}{1 - \tan A \cdot \tan B}33 Now, tan(A+B)=tanA+tanB1tanAtanB\tan(A+B) = \frac{\tan A + \tan B}{1 - \tan A \cdot \tan B}44 tan(A+B)=tanA+tanB1tanAtanB\tan(A+B) = \frac{\tan A + \tan B}{1 - \tan A \cdot \tan B}55 tan(A+B)=tanA+tanB1tanAtanB\tan(A+B) = \frac{\tan A + \tan B}{1 - \tan A \cdot \tan B}66
  2. Substitute values into identity: Now we have tanA=2021\tan A = \frac{20}{21} and tanB=512\tan B = \frac{5}{12}. We can substitute these values into the identity for tan(A+B)\tan(A+B). \newlinetan(A+B)=(tanA+tanB)(1tanAtanB)\tan(A+B) = \frac{(\tan A + \tan B)}{(1 - \tan A \cdot \tan B)}\newlinetan(A+B)=(2021+512)(1(2021512))\tan(A+B) = \frac{(\frac{20}{21} + \frac{5}{12})}{(1 - (\frac{20}{21} \cdot \frac{5}{12}))}
  3. Simplify numerator and denominator: Simplify the numerator and the denominator separately.\newlineFor the numerator:\newlinetanA+tanB=2021+512\tan A + \tan B = \frac{20}{21} + \frac{5}{12}\newlineTo add these fractions, find a common denominator, which is 21×12=25221 \times 12 = 252.\newline(2021)×(1212)+(512)×(2121)=240252+105252\left(\frac{20}{21}\right) \times \left(\frac{12}{12}\right) + \left(\frac{5}{12}\right) \times \left(\frac{21}{21}\right) = \frac{240}{252} + \frac{105}{252}\newline=240+105252= \frac{240 + 105}{252}\newline=345252= \frac{345}{252}\newlineFor the denominator:\newline1(2021×512)=11002521 - \left(\frac{20}{21} \times \frac{5}{12}\right) = 1 - \frac{100}{252}\newlineTo subtract these fractions, express 11 as 252252\frac{252}{252}.\newline(252252)100252=252100252\left(\frac{252}{252}\right) - \frac{100}{252} = \frac{252 - 100}{252}\newline=152252= \frac{152}{252}
  4. Divide to find tan(A+B)\tan(A+B): Now we can divide the numerator by the denominator to find tan(A+B)\tan(A+B).tan(A+B)=345252/152252\tan(A+B) = \frac{345}{252} / \frac{152}{252}When dividing by a fraction, multiply by the reciprocal of the divisor.tan(A+B)=345252×252152\tan(A+B) = \frac{345}{252} \times \frac{252}{152}The 252252 in the numerator and denominator cancel out.tan(A+B)=345152\tan(A+B) = \frac{345}{152}
  5. Simplify final fraction: Simplify the fraction 345152\frac{345}{152} if possible.\newline345345 and 152152 have no common factors other than 11, so the fraction is already in its simplest form.

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