Q. If cosA=257 and tanB=43 and angles A and B are in Quadrant I, find the value of tan(A+B).Answer:
Find tanA: Use the identity for the tangent of the sum of two angles: tan(A+B)=1−tanA⋅tanBtanA+tanB. First, we need to find tanA. Since we know cosA=257 and A is in Quadrant I, we can find sinA using the Pythagorean identity sin2A+cos2A=1.sin2A=1−cos2Asin2A=1−(257)2sin2A=1−62549tan(A+B)=1−tanA⋅tanBtanA+tanB0tan(A+B)=1−tanA⋅tanBtanA+tanB1tan(A+B)=1−tanA⋅tanBtanA+tanB2tan(A+B)=1−tanA⋅tanBtanA+tanB3Now, tan(A+B)=1−tanA⋅tanBtanA+tanB4.
Substitute values into identity: Now we have tanA=724 and tanB=43. We can substitute these values into the identity for tan(A+B).tan(A+B)=(1−tanA⋅tanB)(tanA+tanB)tan(A+B)=(1−(724⋅43))(724+43)
Simplify numerator and denominator: Simplify the numerator and the denominator separately.For the numerator:tanA+tanB=724+43To add these fractions, find a common denominator, which is 28.tanA+tanB=7×424×4+4×73×7tanA+tanB=2896+2821tanA+tanB=2896+21tanA+tanB=28117For the denominator:1−tanA×tanB=1−(724×43)1−tanA×tanB=1−(2872)1−tanA×tanB=2828−28721−tanA×tanB=28−44
Divide to find tan(A+B): Now, divide the numerator by the denominator to find tan(A+B).tan(A+B)=28117/(−2844)When dividing by a fraction, multiply by the reciprocal of the denominator.tan(A+B)=28117×(−4428)The 28s cancel out.tan(A+B)=−44117Simplify the fraction by dividing both the numerator and the denominator by their greatest common divisor, which is 1 in this case.tan(A+B)=−44117
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