# page 69 EXAMPLE 6
reset()
def verify(y1, y2):
    if diff(diff(y1)) + y1 == 0 and diff(diff(y2)) + y2 == 0:
        return 'solution'
    else:
        return 'not a solution'
def solve(y1, y2):
    if diff(y1/y2) == 0:
        return 'const'
    else:
        return 'not a const'
print verify(cos(x), sin(x))
print solve(cos(x), sin(x))