Objectives

• Identify the sides of right-angled triangles

• Calculate complementary angle of right-angled triangles

Name Sides in Right-Angled Triangles

• The Hypotenuse

• The opposite side

• The adjacent side

Complementary Angles

• The three angles in any triangle add to 180°.

• Since one angle in a right-angled triangle measures 90°, the other two angles must add to 90° to make up the 180°.

• The two acute angles in any right-angled triangle are complementary angles (ie add to 90°).

Label Sides

• Use the two CAPITAL letters at its ends.

• Use one lower case letter which matches the opposite vertex (corner).

• Side GH can be called f.

Using sin, cos or tan to find the side or angle of a right triangle.

• Identify the sides or angles

• Choose the right trig ratio based on what was given.

• Solve the equation to find the unknown

Trigonometric Ratios

Remember, each of these ratios relies on you identifying the sides of the triangle based on your reference angle.

Steps to solving for a missing triangle side:

• Identify which 2 sides are "given"

• Which trig ratio goes with those sides?

• Set up a proportion

• Solve your proportion