Cos 42 Degrees

Sin, Cos, Tan, Cot of an Angle
Function
Angle (°)

What is cos 42°?

Answer

cos 42° ≈
0.7431

Angle in radians: 42° = 7π/30. The point of the angle is in quadrant I, where cosine is positive.

≈ — rounded to 4 decimal places. An exact form of cos 42° in square roots exists, but it is unwieldy — nested radicals.

P(cos 42°, sin 42°) ≈ (0.7431, 0.6691)

xyOP

P(cos 42°, sin 42°) ≈ (0.7431, 0.6691)

Highlighted: the projection on the x-axis — cosine, x ≈ 0.7431.

All four functions of 42°
FunctionExact valueDecimal
sin 42°—≈ 0.6691
cos 42°—≈ 0.7431
tan 42°—≈ 0.9004
cot 42°—≈ 1.1106

See Also

Recalculate with different values ↑

Cosine of nearby angles

Anglecos
39°≈ 0.7771
40°≈ 0.7660
41°≈ 0.7547
42°≈ 0.7431
43°≈ 0.7314
44°≈ 0.7193
45°√2/2

FAQ

What is cos 42°?

cos 42° ≈ 0.7431

Is there an exact value of cos 42°?

Yes: 42° is a multiple of 3°, and the values of such angles can be written with square roots — but the expression is unwieldy, with nested radicals built from the values of 18° and 15° (3° = 18° − 15°). In practice the decimal is used: cos 42° ≈ 0.7431.

Why does a calculator show −0.4000 for cos 42?

The calculator is in radian mode (RAD): it takes cos 42 as the cosine of 42 radians, cos 42 rad ≈ −0.4000. Switch it to degrees (DEG): cos 42° ≈ 0.7431. In radians the value is never undefined: π is irrational, so a whole number of radians never lands exactly on an axis.

See Also