Cos 155 Degrees

The value of cos 155 degrees is -0.9063077. . .. Cos 155 degrees in radians is written as cos (155° × π/180°), i.e., cos (31π/36) or cos (2.705260. . .). In this article, we will discuss the methods to find the value of cos 155 degrees with examples.

• Cos 155°: -0.9063077. . .
• Cos (-155 degrees): -0.9063077. . .
• Cos 155° in radians: cos (31π/36) or cos (2.7052603 . . .)

What is the Value of Cos 155 Degrees?

The value of cos 155 degrees in decimal is -0.906307787. . .. Cos 155 degrees can also be expressed using the equivalent of the given angle (155 degrees) in radians (2.70526 . . .)

We know, using degree to radian conversion, θ in radians = θ in degrees × (pi/180°)
⇒ 155 degrees = 155° × (π/180°) rad = 31π/36 or 2.7052 . . .
∴ cos 155° = cos(2.7052) = -0.9063077. . .

Explanation:

For cos 155 degrees, the angle 155° lies between 90° and 180° (Second Quadrant). Since cosine function is negative in the second quadrant, thus cos 155° value = -0.9063077. . .
Since the cosine function is a periodic function, we can represent cos 155° as, cos 155 degrees = cos(155° + n × 360°), n ∈ Z.
⇒ cos 155° = cos 515° = cos 875°, and so on.
Note: Since, cosine is an even function, the value of cos(-155°) = cos(155°).

Methods to Find Value of Cos 155 Degrees

The cosine function is negative in the 2nd quadrant. The value of cos 155° is given as -0.90630. . .. We can find the value of cos 155 degrees by:

• Using Trigonometric Functions
• Using Unit Circle

Cos 155° in Terms of Trigonometric Functions

Using trigonometry formulas, we can represent the cos 155 degrees as:

• ± √(1-sin²(155°))
• ± 1/√(1 + tan²(155°))
• ± cot 155°/√(1 + cot²(155°))
• ±√(cosec²(155°) - 1)/cosec 155°
• 1/sec 155°

Note: Since 155° lies in the 2nd Quadrant, the final value of cos 155° will be negative.

We can use trigonometric identities to represent cos 155° as,

• -cos(180° - 155°) = -cos 25°
• -cos(180° + 155°) = -cos 335°
• sin(90° + 155°) = sin 245°
• sin(90° - 155°) = sin(-65°)

Cos 155 Degrees Using Unit Circle

To find the value of cos 155 degrees using the unit circle:

• Rotate ‘r’ anticlockwise to form 155° angle with the positive x-axis.
• The cos of 155 degrees equals the x-coordinate(-0.9063) of the point of intersection (-0.9063, 0.4226) of unit circle and r.

Hence the value of cos 155° = x = -0.9063 (approx)

☛ Also Check:

• cos 210 degrees
• cos 270 degrees
• cos 11 degrees
• cos 600 degrees
• cos 155 degrees
• cos 80 degrees

FAQs on Cos 155 Degrees

What is Cos 155 Degrees?

Cos 155 degrees is the value of cosine trigonometric function for an angle equal to 155 degrees. The value of cos 155° is -0.9063 (approx)

What is the Value of Cos 155° in Terms of Cosec 155°?

Since the cosine function can be represented using the cosecant function, we can write cos 155° as -[√(cosec²(155°) - 1)/cosec 155°]. The value of cosec 155° is equal to 2.36620.

What is the Value of Cos 155 Degrees in Terms of Tan 155°?

We know, using trig identities, we can write cos 155° as -1/√(1 + tan²(155°)). Here, the value of tan 155° is equal to -0.466307.

How to Find the Value of Cos 155 Degrees?

The value of cos 155 degrees can be calculated by constructing an angle of 155° with the x-axis, and then finding the coordinates of the corresponding point (-0.9063, 0.4226) on the unit circle. The value of cos 155° is equal to the x-coordinate (-0.9063). ∴ cos 155° = -0.9063.

How to Find Cos 155° in Terms of Other Trigonometric Functions?

Using trigonometry formula, the value of cos 155° can be given in terms of other trigonometric functions as:

• ± √(1-sin²(155°))
• ± 1/√(1 + tan²(155°))
• ± cot 155°/√(1 + cot²(155°))
• ± √(cosec²(155°) - 1)/cosec 155°
• 1/sec 155°

☛ Also check: trigonometry table