Examine the equations given in problems 1–4, and show that the functions f(x) = cos(x) and g(x) = tan(x) are not
linear transformations by demonstrating that they do not satisfy the conditions indicated for al real numbers. then, find
values of x and/or y for which the statement holds true.
1. cos(x + y) = cos(x) + cos(y)
2. cos(2x) = 2 cos(x)
3. tan(x + y) = tan(x) + tan(y) 4. tan(2x) = 2 tan(x)