Answer:
(b) 150 feet
Explanation:
You want to know the height of a kite at the end of 225 feet of string, flying at an angle of elevation of 45°.
Right triangle
The 45° angle in the given right triangle tells you this is one of the "special" right triangles. Its side lengths have the ratios ...
1 : 1 : √2
where √2 is the hypotenuse.
That means the other two legs of this right triangle are ...
(225 ft)/√2 ≈ 159.099 ft
Rounded to the nearest 50 feet, this is about 150 feet.
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Additional comment
The sine function relates the angle value to the opposite side:
Sin = Opposite/Hypotenuse
Opposite = Hypotenuse · Sin
height = (225 ft)·sin(45°) = 225 ft/√2 ≈ 159.099 ft