Answer: C. Definition of an Altitude
Step-by-step explanation:
Given: In triangle MNO shown below, segment NP is an altitude from the right angle.
Let ∠MNP=x
Then ∠PNO=90°-x
Therefore in triangle MNO,
∠MPN=∠NPO =90° [by definition of Altitude]
[Definition of altitude : A line which passes through a vertex of a triangle, and joins the opposite side forming right angles. ]
Now using angle sum property in ΔMNP
∠MNP+∠MPN+∠PMN=180°
⇒x+90°+∠PMN=180°
⇒∠PMN=180°-90°-x
⇒∠PMN=90°-x
Now, in ΔMNO and ΔPNO
∠PMN=∠PNO=90°-x
and ∠MPN=∠NPO =90° [by definition of altitude]
Therefore by AA similarity postulate, we have
ΔMNO ≈ ΔPNO
2+2=4
a^2+b^2=c^2
15^2-4^2
=225-16
=209
The correct answer is x = 20
