Find the value of tan 78° 27'
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Tan 78°
Welcome to tan 78°, our post aboutthe tangent of 78 degrees.
For the tangent of 78 degrees we use the abbreviation tan for the trigonometric function together with the degree symbol °, and write it as tan 78°.
If you have been looking for what is tan 78°, or if you have been wondering about tan 78 degrees in radians, then you are right here, too.
In this post you can find the tan 78° value, along with identities.
Read on to learn all about the tan of 78°.
Tan 78 Degrees
If you want to know what is tan 78 degrees in terms of trigonometry, then navigate straight to the explanations in the next paragraph; what’s ahead in this section is the value of tan 78°:
tan78° = 4.70463
tan 78° = 4.70463
tan 78 degrees = 4.70463

The tan of 78 degrees is 4.70463, the same as tan of 78 degrees in radians. To obtain 78 degrees in radian multiply 78° by π / 180° = 13/30 π. Tan 78degrees = tan (13/30 × π).
Our results of tan78° have been rounded to five decimal places. If you want tangent 78° with higher accuracy, then use the calculator below; our tool displays ten decimal places.
To calculate tan 78 degrees insert the angle 78 in the field labelled °, but if you want to calculate tan 78 in radians, then you have to press the swap unit button first.
Calculate tan [degrees]
° :
Swap Units
value :
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The identities of tangent 78° are as follows:
tan78°
= cot (90°-78°) = cot 12°
-tan78°
= tan (-78°) = -tan 78°
= cot (90°+78°) = cot 168°
= tan (180°-78°) = tan 102°
Note that tan78° is periodic: tan (78° + n × 180°) = tan 78 degrees, n∈Z.
There are more formulas for the double angle (2 × 78°), half angle ((78/2)°) as well as the sum, difference and products of two angles such as 78° and β.
You can locate all of them in the respective article found in the header menu. To find everything about tan -78° click the link. And here is all about cot 78°, including, for instance, a converter.
In terms of the other five trigonometric functions, tan of 78° =
±sin78∘1–sin278∘
±1–cos278∘cos78∘
±sec278∘−1
±1csc278∘–1
1cot78∘
As the cotangent function is the reciprocal of the tangent function, 1 / cot 78° = tan78°.
In the next part of this article we discuss the trigonometric significance of tan78°, and there you can also learn what the search calculations form in the sidebar is used for.
What is tan 78°?
In a triangle which has one angle of 90 degrees, the tangent of the angle of 78° is the ratio of the length of the opposite side o to the length of the adjacent side a: tan 78° = o/a.
In a circle with the radius r, the horizontal axis x, and the vertical axis y, 78 degrees is the angle formed by the two sides x and r; r moving counterclockwise is the positive angle.
Applying the unit-circle definition found on our homepage, assumed r = 1, in the intersection of the point (x,y) and the circle, y = sin 78°, x = cos 78° and tan 78° = sin 78°/cos 78°.
Bringing together the triangle definition and the unit circle definition of tangent 78 degrees, a = x, o = y and h = r = 1. It follows that y/x=oppositeadjacent=tan78∘.
Note that you can locate many terms including the tangent78° value using the search form. On mobile devices you can find it by scrolling down. Enter, for instance, value of tan78°.
Along the same lines, using the aforementioned form, can you look up terms such as tan 78° value, tan 78, tan78° value and what is the tan of 78 degrees, just to name a few.
Given the periodicity of tangent of 78°, to determine the tangent of an angle > 180°, e.g. 798°, calculate tan 798° as tan (798 Mod 180)° = tangent of 78°, or look it up with