Applying Law of Sines and Law of Cosines to find sides and angles of acute and obtuse triangles.

Acute angle
An angle whose measure is greater than 0 but less than 90 degrees.

Acute triangle
A triangle whose angles are acute.

Cosine
Ratio determined by the hypotenuse in a right triangle and a side adjacent to a reference angle.

Equilateral triangle
A triangle whose sides are equal in length.

Isosceles triangle
A triangle with two sides of equal length.

Proportion
A statement that two ratios are equal

Proportional
One of four numbers that form a true proportion

Sine
Ratio of the length of the opposite side to a reference angle in a right triangle and the hypotenuse. Opposite/hypotenuse.

Obtuse angle
An angle whose measure is greater than 90 but less than 180 degrees

Obtuse triangle
A triangle with one acute angle.

Ratio
A quotient of 2 numbers

Right triangle
A triangle that has a 90 degree angle.

Scalene triangle
A triangle with no equilateral sides.

Triangle
A polygon with three sides.

The sum of the interior angles in a triangle is 180°.

Move any of the vertices in this triangle to verify that sum.

Solving by Law of Sines, or Law of Cosines does not use sine, and cosine the way you

do it with right triangles; nevertheless, you still need to get the inverse of sine,

and cosine. The following applet helps you to understand the relationship

between the trigonometric ratios, and their inverses. Drag any vertex to

view in a dynamic way this relationship.

Solving Acute, and Obtuse Triangles Using Law of Sines, and Law of Cosines.