Question

From the figure given below, What is the angle formed by COA?

• A. Straight angle
• B. Acute angle
• C. Obtuse angle
• D. Right angle

Answer 1

The correct option is C Obtuse angle

Since AB is a straight line, $\angle AOB={180}^{\circ }$

Therefore, $\angle AOC+\angle COB={180}^{\circ }$

$\Rightarrow 4x+{30}^{\circ }+{70}^{\circ }={180}^{\circ }$

$\Rightarrow 4x+{100}^{\circ }={180}^{\circ }$

$\Rightarrow 4x={180}^{\circ }-{100}^{\circ }$

$\Rightarrow 4x={80}^{\circ }$

$\Rightarrow x={20}^{\circ }$

Therefore,

$\angle AOC=4x+{30}^{\circ }={80}^{\circ }+{30}^{\circ }={110}^{\circ }$

Which is 'obtuse angle'