Question

If two angles of a triangle are ${90}^{\circ }$, ${20}^{\circ }$, then what is the third angle?

• A. ${60}^{\circ }$
• B. ${70}^{\circ }$
• C. ${90}^{\circ }$
• D. ${80}^{\circ }$

Answer 1

The correct option is B ${70}^{\circ }$

In a Euclidean space, the $sum$ of measures of these three angles of $anytriangle$ is invariably equal to the straight angle, also expressed as ${180}^o$

Let, the third angle be $x$

$\therefore$ $180=90+20+x$

$x=180-110$

$\therefore x={70}^o$.