Sin 40 Degrees

The value of sin 40 degrees is 0.6427876. . .. Sin 40 degrees in radians is written as sin (40° × π/180°), i.e., sin (2π/9) or sin (0.698131. . .). In this article, we will discuss the methods to find the value of sin 40 degrees with examples.

• Sin 40°: 0.6427876. . .
• Sin (-40 degrees): -0.6427876. . .
• Sin 40° in radians: sin (2π/9) or sin (0.6981317 . . .)

What is the Value of Sin 40 Degrees?

The value of sin 40 degrees in decimal is 0.642787609. . .. Sin 40 degrees can also be expressed using the equivalent of the given angle (40 degrees) in radians (0.69813 . . .).

We know, using degree to radian conversion, θ in radians = θ in degrees × (pi/180°)
⇒ 40 degrees = 40° × (π/180°) rad = 2π/9 or 0.6981 . . .
∴ sin 40° = sin(0.6981) = 0.6427876. . .

Explanation:

For sin 40 degrees, the angle 40° lies between 0° and 90° (First Quadrant). Since sine function is positive in the first quadrant, thus sin 40° value = 0.6427876. . .
Since the sine function is a periodic function, we can represent sin 40° as, sin 40 degrees = sin(40° + n × 360°), n ∈ Z.
⇒ sin 40° = sin 400° = sin 760°, and so on.
Note: Since, sine is an odd function, the value of sin(-40°) = -sin(40°).

Methods to Find Value of Sin 40 Degrees

The sine function is positive in the 1st quadrant. The value of sin 40° is given as 0.64278. . .. We can find the value of sin 40 degrees by:

• Using Trigonometric Functions
• Using Unit Circle

Sin 40° in Terms of Trigonometric Functions

Using trigonometry formulas, we can represent the sin 40 degrees as:

• ± √(1-cos²(40°))
• ± tan 40°/√(1 + tan²(40°))
• ± 1/√(1 + cot²(40°))
• ± √(sec²(40°) - 1)/sec 40°
• 1/cosec 40°

Note: Since 40° lies in the 1st Quadrant, the final value of sin 40° will be positive.

We can use trigonometric identities to represent sin 40° as,

• sin(180° - 40°) = sin 140°
• -sin(180° + 40°) = -sin 220°
• cos(90° - 40°) = cos 50°
• -cos(90° + 40°) = -cos 130°

Sin 40 Degrees Using Unit Circle

To find the value of sin 40 degrees using the unit circle:

• Rotate ‘r’ anticlockwise to form a 40° angle with the positive x-axis.
• The sin of 40 degrees equals the y-coordinate(0.6428) of the point of intersection (0.766, 0.6428) of unit circle and r.

Hence the value of sin 40° = y = 0.6428 (approx)

☛ Also Check:

• sin 180 degrees
• sin 270 degrees
• sin 11 degrees
• sin 255 degrees
• sin 240 degrees
• sin 55 degrees

FAQs on Sin 40 Degrees

What is Sin 40 Degrees?

Sin 40 degrees is the value of sine trigonometric function for an angle equal to 40 degrees. The value of sin 40° is 0.6428 (approx).

How to Find Sin 40° in Terms of Other Trigonometric Functions?

Using trigonometry formula, the value of sin 40° can be given in terms of other trigonometric functions as:

• ± √(1-cos²(40°))
• ± tan 40°/√(1 + tan²(40°))
• ± 1/√(1 + cot²(40°))
• ± √(sec²(40°) - 1)/sec 40°
• 1/cosec 40°

☛ Also check: trigonometric table

How to Find the Value of Sin 40 Degrees?

The value of sin 40 degrees can be calculated by constructing an angle of 40° with the x-axis, and then finding the coordinates of the corresponding point (0.766, 0.6428) on the unit circle. The value of sin 40° is equal to the y-coordinate (0.6428). ∴ sin 40° = 0.6428.

What is the Value of Sin 40 Degrees in Terms of Tan 40°?

We know, using trig identities, we can write sin 40° as tan 40°/√(1 + tan²(40°)). Here, the value of tan 40° is equal to 0.839099.

What is the Exact Value of sin 40 Degrees?

The exact value of sin 40 degrees can be given accurately up to 8 decimal places as 0.64278760.