An exterior angle of a triangle is equal to the sum of the two interior angles that are opposite:

d° = b° + c°

To find angle c, remember that the sum of the interior angles of a triangle is 180°:

180° = a° + b° + c°
c° = 180° - a° - b°
c° = 180° - 43° - 26° = 111°

So, d° = 26° + 111° = 137°

A shortcut to get this answer is to remember that angles around a line add up to 180°:

a° + d° = 180°
d° = 180° - a°
d° = 180° - 43° = 137°

The area of a triangle is equal to ½ base x height:

a = ½bh
a = ½ x 3 x 1 = \( \frac{3}{2} \) = 1\(\frac{1}{2}\)

To solve this equation, isolate the variable for which you are solving (c) on one side of the equation and put everything else on the other side.

2c + 4z = -8c - 9z - 6
2c = -8c - 9z - 6 - 4z
2c + 8c = -9z - 6 - 4z
10c = -13z - 6
c = \( \frac{-13z - 6}{10} \)
c = \( \frac{-13z}{10} \) + \( \frac{-6}{10} \)
c = -1\(\frac{3}{10}\)z - \(\frac{3}{5}\)

A triangle is a three-sided polygon. It has three interior angles that add up to 180° (a + b + c = 180°). An exterior angle of a triangle is equal to the sum of the two interior angles that are opposite (d = b + c). The perimeter of a triangle is equal to the sum of the lengths of its three sides, the height of a triangle is equal to the length from the base to the opposite vertex (angle) and the area equals one-half triangle base x height: a = ½ base x height.

A quadrilateral is a shape with four sides. The perimeter of a quadrilateral is the sum of the lengths of its four sides.