Cosine Calculator

cos(60 degrees) = 0.5 exactly. This comes from the 30-60-90 special triangle where the adjacent side is half the hypotenuse. It is one of the most commonly used values in trigonometry and physics.

cos(20) = 0.9397, cos(30) = 0.8660, cos(38) = 0.7880, cos(45) = 0.7071, cos(60) = 0.5, cos(90) = 0, cos(120) = -0.5, cos(180) = -1. As an example, 1.5 / cos(38) = 1.5 / 0.7880 = 1.904, useful for resolving force or distance components in physics.

cos^-1, also written arccos, gives you the angle whose cosine equals a given ratio. For example, cos^-1(0.5) = 60 degrees, cos^-1(8.9/11) = arccos(0.809) is about 36 degrees, and cos^-1(6.1/8.8) = arccos(0.693) is about 46 degrees. Use the linked arccos calculator for inverse cosine values; this calculator computes forward cosine only.

The five essential values: cos(0) = 1, cos(30) = 0.8660, cos(45) = 0.7071, cos(60) = 0.5, cos(90) = 0. Notice cosine values decrease from 1 to 0 as the angle increases from 0 to 90 degrees, which is the opposite pattern of sine.

Cosine is negative in quadrant II (90 to 180 degrees) and quadrant III (180 to 270 degrees). For example, cos(120) = -0.5 and cos(180) = -1. Cosine is positive in quadrants I (0-90) and IV (270-360).

In a right triangle, sine uses the opposite side (sin = opposite / hypotenuse) while cosine uses the adjacent side (cos = adjacent / hypotenuse). They are complements: cos(theta) = sin(90 - theta). The cosine graph is the same shape as the sine graph, shifted 90 degrees to the left.

Yes. Cosine has a period of 360 degrees, so cos(420) = cos(60) = 0.5. The calculator accepts any angle, including negative values: cos(-60) = cos(60) = 0.5 because cosine is an even function.

Yes, the Cosine Calculator is fully embeddable. Tap "Embed" above to configure appearance and copy the code. It is free to use, works on any platform (HTML, WordPress, CMS), and adjusts to any screen size automatically. Visit calculory.com/services/embed-calculators for the complete guide.