`sec^2theta=(4x y)/((x+y)^2)` is true if and only if `x+y!=0` (b) `x=y ,x!=0` `x=y` (d) `x!=0,y!=0`

Explanation

To solve the equation \( \sec^2 \theta = \frac{4xy}{(x+y)^2} \) and determine the conditions under which it is true, we can follow these steps:

### Step 1: Understand the properties of secant
The secant function is defined as:
\[ \sec^2 \theta \geq 1 \]
This means that the right-hand side of the equation must also be greater than or equal to 1:
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