Definite Integral of Multiplied 2 Trigonometric Functions

Before you see this post,

see

Integral Some Functions

Synthesis of Trigonometric Functions

Differential of A Function : sin x, cos x

Before you see this post,

see

A Property of Limit of A Function : f(x)/g(x)

A Property of Limit of A Function : f(x)g(x)

Synthesis of Trigonometric Functions

Synthesis of Trigonometric Functions

Before you see this post,

see

Distance between A Point and A line

and

Sum and Products by Unit Vector

Limit of sin(x)/x and tan(x)/x

Before you see this post,

see

A Property of Limit of A Function : f(x)/g(x),

Trigonometric Function : Sine, Cosine and Tangent,

Graph of Trigonometric Function : Sine, Cosine and Tangent

and

Radian

First, Let's divide the formula by sinθ.

There is a result.

Second, Let's divide the formula by tanθ. 

There is a result.

Radian

Graph of Trigonometric Function : Sine, Cosine and Tangent

Before you see this post,

see

Trigonometric Function : Sine, Cosine and Tangent

Trigonometric Function : Sine, Cosine and Tangent

               In Right-angled triangle, they are defined like the picture below.

sine -> sin

cosine -> cos

tangent -> tan

In Cartesian coordinate system, 

we can notate trigonometric functions, sine, cosine and tangent, 

like the picture above.