Question

a+b=90 so the what is the minimum and maximum value of (cosa.cosb)​

Answer 1

assume that a=45 and b= 45 then a+b=90
(cos a.cos b)

(cos45.cos45) [cos 45 = 1/^root 2]

(1/^root2 . 1/^root2) [by cross multiplication]

(root 2/ root2) [now cancel them]

ANS :-1

Answer 2

Answer:

Step-by-step explanation:

A+B=90 that implies

B=90-A that implies

cosAcosB=cosA.cos(90-A)=cosA.sinA

multiply and divide by 2

1/2(2sinAcosA)=1/2(sin2A)

-1≤sin2A≤1 that implies

-1/2≤1/2(sin2A)≤1/2

so the maximum and minimum values are -1/2,1/2 respectively