Practicing Success
Points $\mathrm{A}$ and $\mathrm{B}$ are on a circle with centre $\mathrm{O}$. Point $\mathrm{C}$ is on the major arc $\mathrm{AB}$. If $\angle \mathrm{OAC}=35^{\circ}$ and $\angle \mathrm{OBC}=45^{\circ}$, then what is the measure (in degrees) of the angle subtended by the minor arc $\mathrm{AB}$ at the centre? |
70 160 80 100 |
160 |
In \(\Delta \)OAC = OA = OC (radius) So, \(\angle\)OAC = \(\angle\)OCA = \({35}^\circ\) Also, In \(\Delta \)OBC = OB = OC (radius) So, \(\angle\)OBC = \(\angle\)OCB = \({45}^\circ\) = \(\angle\)ACB = \(\angle\)OCA + \(\angle\)OCB = 35 + 45 = 80 We know that angle subtended by an arc on the center of the circle is twice the angle subtended by it on any other part of the circle. = \(\angle\)AOB = 2 x \(\angle\)ACB = 2 x 80 = \({160}^\circ\) Therefore, answer is \({160}^\circ\). |