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28. If sin a.sin ß-cosa.cosB =1, show that tan a+tan B=0.​

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Answer:

Hey BUDDY here's ur answer

sinAsinB - cosAcosB = 1 <--- given

cosAcosB - sinAsinB = -1 <--- multiplies both sides by -1

cos(A+B) = -1 <--- angle addition FORMULA for COSINE

A+B is an odd multiple of pi <--- cosine function is -1 at 180=pi, 540 = 3*pi, 900=*5*pi, etc

sin(A+B)=0 <-- SINE function is zero at odd multiples of pi

sinAcosB + sinBcosA = 0 <--- angle addition formula for sine

sinA/cosA + sinB/cosB = 0 <--- divides both sides by cosA*cosB

tanA + tanB = 0 <--- TAN = sin/cos



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