Khan Academy Static

Introduction_to_the_Pythagorean_trigonometric_identity

Learn about a very special trigonometric identity that follows from the Pythagorean theorem.

Sine_and_cosine_of_complementary_angles

Learn about the relationship between the sine of an angle and the cosine of its complementary angle, which is the angle that completes to 90°.

Introduction_to_the_trigonometric_ratios

Meet your new best friends: sine, cosine, and tangent.

Solving_for_an_angle_in_a_right_triangle_using_the_trigonometric_ratios

Learn how to find an acute angle in a right triangle when given two side lengths.

Modeling_with_right_triangles

Solve real-world problems that can be modeled by right triangles, using trigonometry.

Trigonometric_ratios_and_similarity

Learn how the trigonometric ratios are derived from triangle similarity considerations.

Solving_for_a_side_in_a_right_triangle_using_the_trigonometric_ratios

Learn how to find a side length in a right triangle when given one side length and one acute angle.

The_reciprocal_trigonometric_ratios

Learn about the remaining three side ratios in a right triangle: the secant, the cosecant, and the cotangent.

Trigonometric_ratios_of_special_triangles

Learn to find the sine, cosine, and tangent of 45-45-90 triangles and also 30-60-90 triangles.