Answer:
300 in²
Explanation:
You want the area of a TV screen with a 25-inch diagonal and a 15-inch height.
Pythagorean theorem
To find the area, you need to know the screen width. You can find it using trigonometry, but it is probably more straightforward to find it using the Pythagorean theorem. That tells you the square of the diagonal is the sum of the squares of the height and width:
w² +15² = 25²
w² = 625 -225 = 400
w = √400 = 20 . . . . inches
Area
The area of a rectangle 15 inches high and 20 inches wide is ...
A = LW
A = (20 in)(15 in) = 300 in²
The area of the screen is 300 square inches.
__
Additional comment
The angle between the side and the diagonal at upper left is ...
cos(α) = 15/25
α = arccos(15/25) ≈ 53.13°
Then the width of the screen is ...
w = 25·sin(53.13°) = 20 . . . . inches