Question

8, sec²A = 4xy/(x + y)² সত্য হবে, যদি এবং কেবলমাত্র যদি
A. x + y + 0 হয় B. x = y, x not equal to 0 হয় C.X = y হয় D. x not equal to 0 , y not equal to 0 হয়।​

Answer 1

Step-by-step explanation:

cosθ

1

=

(x+y)

2

4xy

cosθ

1

=

x+y

2

xy

cosθ=

2

xy

x+y

We know cosθ lies between −1 & 1

−1≤

2

xy

x+y

≤1 …….(1)

AM≥Gm

for x & y ⇒

2

x+y

≥

xy

2

xy

x+y

≥1 ………(2)

From (1) & (2)

2

xy

x+y

=1

(x+y)

2

=4xy

⇒(x−y)

2

=0

∴x=y

∴ Infinite solutions. [x±0,y±0].