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23,If tanAn tanB and sinAm sinB.Prove that cosa = m-rr1 |
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Answer» sinA = msinB....(1) tanA= ntanB (sinA/cosA) = n(sinB/cosB)....(2) substuting sinB value from equation (1) cosB = (n/m) cosA......(3) sin^2A = m^2sin^2B 1-cos^2A = m^2(1-cos^2B) substituting equation (3) 1-cos^2A = m^2[1 – ((n^2/m^2)cos^2A)] 1 – cos^2A = m^2– n^2cos^2A n^2cos^2A – cos^2A = m^2– 1 cos^2A = (m^2– 1)/(n^2– 1) |
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