What is acute angle explain with diagram.

What is the number of obtuse angles in the given figure?

What is the measure of a right angle? 

In the given figure, two straight line $AB$ and $CD$ intersect at a point $O$. If $\angle AOC = 42°$, find the measure of the angles $\angle AOD, \angle BOD \& \angle COB$.

In the following figure, is $\mathit{\angle }1\mathit{}$ adjacent to $\mathit{\angle }2$? Give reasons.

In the given figure, $AOB$ is a straight line and the ray $OC$ stands on it. If $\angle AOC=64°$ and $\angle BOC=x°$, find the value of $x$.

In the given figure, $\mathbf{\angle }1\mathbf{}$ and $\mathbf{}\mathbf{\angle }2\mathbf{}$ are supplementary angles. If $\mathit{\angle }1$ is decreased, what changes should take place in $\mathit{\angle }2$ so that both the angles still remain supplementary.