cosd — Compute cosine of degree-valued inputs in MATLAB and RunMat.
y = cosd(x) evaluates cosine element-wise in degrees. MATLAB documents single and double real or complex arrays; RunMat mode additionally admits typed integers, logicals, and characters through explicit compatibility gates.
Syntax
Y = cosd(X)Inputs
| Name | Type | Required | Default | Description |
|---|---|---|---|---|
X | Any | Yes | — | Input scalar, array, logical array, complex value, or gpuArray. |
Returns
| Name | Type | Description |
|---|---|---|
Y | Any | Element-wise cosine result with degree input semantics. |
Errors
| Identifier | When | Message |
|---|---|---|
RunMat:cosd:InvalidInput | Input cannot be interpreted as supported numeric/logical/complex data. | cosd: invalid input |
RunMat:cosd:Internal | Internal gather/conversion/allocation flow failed. | cosd: internal error |
How cosd works
- Operates element-wise on scalars, vectors, matrices, and N-D tensors.
- Single real and complex inputs preserve single output; double inputs preserve double output.
- Typed integers are a RunMat-only extension. All eight real integer classes require exact binary64 representability before degree reduction and produce double output; aligned values above
flintmaxare accepted when their significant bits fit binary64. - Logical and character inputs are separately gated RunMat-only extensions and produce double output.
- Returns exactly 0 at multiples of 90 and exactly ±1 at multiples of 180.
- Returns exactly ±0.5 at multiples of 60 and 120.
- Complex inputs delegate to the analytic extension of
cosafter scaling bypi/180; exact-value treatment for complex operands is deferred. - Output shape matches the input shape; non-finite inputs propagate as
NaN. - String inputs are unsupported and raise a builtin-scoped error.
- Table, timetable, tall, and distributed container inputs remain general RunMat container/runtime gaps rather than integer-storage gaps.
Examples
Cosine of a canonical degree angle
y = cosd(60)Expected output:
y = 0.5Cosine of multiples of 90 returns exactly zero
y = cosd([90 270])Expected output:
y = [0 0]Cosine of a vector of common angles
angles = [0 30 45 60 90];
y = cosd(angles)Expected output:
y = [1 0.8660 0.7071 0.5 0]Using cosd with coding agents
Open a RunMat example with live inputs, then ask the agent to explain how cosd changes the result.
Run a small cosd example, explain the result, then change one input and compare the output.
FAQ
Why does cosd(90) return exactly zero?⌄
MATLAB guarantees an exact zero at multiples of 90 to avoid floating-point noise from pi. RunMat reduces the angle modulo 360 and short-circuits the canonical cases before delegating to cos.
Is cosd(x) equivalent to cos(x*pi/180)?⌄
Mathematically yes, but the floating-point result differs at canonical angles because pi/180 is not exact in binary floating point. cosd returns the exact MATLAB values at multiples of 60, 90, 120, and 180.
Does cosd support arrays?⌄
Yes. Scalars, vectors, matrices, and N-D tensors are all handled element-wise; the shape of the input is preserved.
Related Math functions
Trigonometry
acos · acosh · asin · asinh · atan · atan2 · atanh · cos · cosh · cospi · deg2rad · pol2cart · rad2deg · sin · sind · sinh · sinpi · tan · tand · tanh
Elementwise
abs · angle · bsxfun · complex · conj · double · erf · erfcinv · exp · expm1 · factorial · flintmax · gamma · gammaln · heaviside · hypot · idivide · imag · intmax · intmin · ldivide · log · log10 · log1p · log2 · minus · nextpow2 · plus · pow2 · power · rdivide · real · realmax · realmin · realsqrt · rescale · sign · single · sqrt · swapbytes · times · typecast · uint16 · uint32 · uint8
Reduction
all · any · bounds · cummax · cummin · cumprod · cumsum · cumtrapz · diff · gradient · max · maxk · mean · median · min · mink · movmax · movmean · movmedian · movmin · movprod · movstd · movsum · movvar · nnz · prod · rms · std · sum · trapz · var
Structure
bandwidth · isdiag · ishermitian · issymmetric · istril · istriu · symrcm
Signal
blackman · butter · buttord · cheb2ord · conv · conv2 · deconv · downsample · envelope · filter · filtfilt · fir1 · freqz · gauspuls · hamming · hann · hilbert · periodogram · pulstran · pwelch · rectpuls · resample · sawtooth · sinc · spectrogram · square · tripuls · unwrap · upsample · zplane
Optim
coneprog · fminbnd · fminunc · fsolve · fzero · integral · linprog · lsqcurvefit · lsqnonlin · optimoptions · optimset · quad · secondordercone
Ops
cross · ctranspose · dot · mldivide · mpower · mrdivide · mtimes · pagemtimes · pagetranspose · trace · transpose
Open-source implementation
Unlike proprietary runtimes, every RunMat function is open-source. Read exactly how cosd is executed, line by line, in Rust.
- View the source for cosd in Rust on GitHub
- Learn how the RunMat runtime works
- Found a bug? Open an issue with a minimal reproduction.
About RunMat
RunMat is an open-source runtime that executes MATLAB-syntax code blazing on any GPU. It is licensed under the Apache 2.0 license.
- RunMat automatically optimizes your math for GPU execution on Apple, Nvidia, and AMD hardware. No code changes needed. Simulations that took hours now take minutes.
- Start running code in seconds. RunMat runs in the browser, on the desktop, or from the CLI. No license server, no IT ticket.