Q. If sinA=419 and cosB=2921 and angles A and B are in Quadrant I, find the value of tan(A−B).Answer:
Find cosA: Use the Pythagorean identity to find cosA.cosA=1−sin2AcosA=1−(419)2cosA=1−168181cosA=16811600cosA=4140
Find sinB: Use the Pythagorean identity to find sinB. sinB=1−cos2B sinB=1−(2921)2 sinB=1−841441 sinB=841400 sinB=2920
Find tan(A−B): Use the angle difference identity for tangent to find tan(A−B).tan(A−B)=1+tanA⋅tanBtanA−tanBtanA=cosAsinA=40/419/41=409tanB=cosBsinB=21/2920/29=2120tan(A−B)=1+(409)⋅(2120)(409)−(2120)
Simplify tan(A−B): Simplify the expression for tan(A−B). tan(A−B)=1+(409)⋅(2120)(409)−(2120) tan(A−B)=40⋅21(9⋅21)−(20⋅40)/(1+40⋅219⋅20) tan(A−B)=840189−800/(1+840180) tan(A−B)=840−611/(1+840180) tan(A−B)=840−611/(840840+180) tan(A−B)=840−611/(8401020) tan(A−B)=840−611⋅1020840 tan(A−B)=1020−611 tan(A−B)=1020−611
Simplify fraction: Simplify the fraction−611/1020. Both the numerator and the denominator can be divided by 61. tan(A−B)=−611/1020tan(A−B)=−10/17
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