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MathNet 2026 — Part 08 Question 35

Math Olympiad Vault · MathNet 2026 — Part 08

Question 35

Circles $w_1$ and $w_2$ with centers $O_1$ and $O_2$ respectively intersect in points $A$ and $B$. A straight line $O_1O_2$ intersects $w_1$ in a point $Q$, that is not inside $w_2$, and $w_2$ in a point $X$, that is inside $w_1$. Around the triangle $O_1AX$ a circle $w_3$ is circumscribed and intersects $w_1$ for the second time in a point $T$. A straight line $QT$ intersects $w_3$ in a point $K$, and a straight line $QB$ intersects $w_2$ a second time in a point $H$. Prove that

Question illustration

Fig. 24


a) points $T$, $X$, $B$ are collinear;

b) points $K$, $X$, $H$ are collinear.