WAEC 2015 Mathematics · Question 36
PQRS is a square. If x is the midpoint of PQ, calculate correct to the nearest degree, <PXS.
Options
- A.53o
- B.55o
- C.63o
- D.65o
Answer: C. 63o
Explanation written with AI and checked against the answer key
Analyze the question: PQRS is a square and X is the midpoint of PQ. We need the angle PXS, which lies in triangle PXS.
Concept: In a square, each angle is 90°. Triangle PXS is right-angled at P, so we can use the tangent ratio.
Solution:
Let the side of the square be 2a. Then:
- PS = 2a
- PX = a (X is the midpoint of PQ)
In right-angled triangle PXS (right angle at P), for angle PXS:
- Opposite side = PS = 2a
- Adjacent side = PX = a
tan(PXS) = PS / PX = 2a / a = 2
PXS = tan⁻¹(2) ≈ 63.43°
To the nearest degree, PXS ≈ 63°.
Answer: C (63°)
Tip: When a point is the midpoint of a side of a square, the ratio of the sides in the right-angled triangle is 2 : 1, so tan θ = 2. Remember tan⁻¹(2) ≈ 63.4° (and tan⁻¹(1/2) ≈ 26.6°). They add up to 90°, which is a quick way to check your work.
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