Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2021/iii/paper-137/2/a/solution

The Gamma 1 congruence subgroup is
The space consists of the holomorphic functions satisfying
for every and which are holomorphic at a cusp for every cusp. Its subspace consists of the forms that vanish at every cusp.

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