Trigonometry-1 (XAT-2011) (3-Marks)

What is the maximum possible value of 21Sinx+72Cosx?

(1)21   (2) 57   (3) 63   (4) 75   (5) None of these

Solution follows here:

Solution:

It is a direct trigonometric formula based one.

Maximum value of aSinx+bCosx = √(a²+b²)

√(a²+b²) = √(21²+72²) = √(3² 7²+3² 24²) = 3 √(7²+24²)

= 3 √(49+576) = 3 √625 = 3*25 = 75

Answer (4)