If $tan^2 A - 6 tan A+ 9 = 0$, 0 <A < 90°, What is the value of $6 cot A + 8\sqrt{10} cos A$?
Answer & explanation
Correct answer: option 3
tan2A - 6tanA + 9 = 0
tan2A - 3tanA - 3tanA + 9 = 0
tanA ( tanA - 3 ) - 3 ( tanA - 3 ) = 0
So , tanA - 3 = 0
tanA = 3
P = 3 , B = 1
Using pythagoras theorem ,
P2 + B2 = H2
32 + 12 = H2
H2 = 10
H = √10
Now , 6cotA + 8√10cosA
= 6 × \(\frac{1}{3}\) + 8√10 × \(\frac{1}{√10}\)
= 2 + 8
= 10