## Mathematic Question

- Dalam Rajah 3, CDE ialah tangen kepada bulatan berpusat O pada titik D .

In Diagram 3 , CDE is a tangent to the circle with the centre O at point D.

Cari nilai x.

Find the value of x.

A 15^{\circ}

C 70^{\circ}

B 35^{\circ}

D 85^{\circ}

### Mathematics Solution

Let the small angle beside x be called as **y**.

Using the Circle’s Theorem, the angle subtended by an arc of a circle at its center is **twice the angle it subtends anywhere on the circle’s circumference**

1.Angle at AOD (center) should be twice the angle at ABD, henceAngle ABD = 35°

2.Outer angle of AOD = 360° - 70° =290°.

3.The quadrilateral, ABDO has a total internal angle of 360°.

4.y (small angle beside x) is equal to 360° - 290° - 35° - 15° = 20°

5.Since CDE is a tangent to the circle, Angle ODE = 90°. Therefore, x = 90° - 20° = 70°.

Therefore, the answer is **C. 70°.**