Unusual Math with incorrect results? [duplicate]

Answer 1

This is being caused by the fact that you are using degrees
and the trigonometric functions expect radians as input:
sin(radians)

The description for sin is:

sin(x)
    Return the sine of x (measured in radians).

In Python, you can convert degrees to radians with the math.radians function.

So if you do this with your input:

>>> math.sin(math.radians(35)) * 15 + 9
17.60364654526569

it gives the same result as your calculator.

Answer 2

cos(35)[degree] = 0.819 * 15 + 9 = 21.285  <-- Your calculator

sin(35)[radian] = -0.428 * 15 + 9 = 2.577  <-- Python

Answer 3

The following Python methods can be used to convert radians to degrees or vice versa:

math.degrees
math.radians

Using your example:

>>> from math import cos, sin, radians
>>> sin(radians(35)) * 15 + 9
17.60364654526569
>>> cos(radians(35)) * 15 + 9
21.28728066433488

Weird calculator... takes degrees but returns radians.