# The variable cannot be assigned a number

I simplify the codes as below:

```
var("T t kx A")
w = 2*pi/T
kt = kx + A*cos(w*t)
hkt = sin(kt)
show(hkt)
hkti = hkt.integral(t)
show(hkti)
```

when I do

```
hkti(t=T)
```

It is OK, but when I want to assign an integer or real number, there is a problem

```
hkti(t=0)
```

or

```
hkti(t=0.0)
```

The error reads:

```
AttributeError: 'sage.rings.integer.Integer' object has no attribute 'variables'
```

or

```
AttributeError: 'sage.rings.real_mpfr.RealLiteral' object has no attribute 'variables'
```

It annoys me, could someone help me on this?

Thanks Xiangru