Hello, may you please help me with the right steps I should take to solve those problems?

STEREOMETRY 1. Let ABCA1BiCi be a triangular prism. Find the angle between: a. AB and CC1 b. AB and CiBi 2. Let ABCDAlBiCID1 be a cube. Find the angle between: cube a. AB and DD1 all sides equal b. AC and DiCi c. BC1 and DD1 d. BD and A1C1 e. BC and CD1 3. Let ABCDAlBICiDi be a right cuboid. Prove that: a. AB and CiDi are parallel; b. AB1 and DC1 are parallel; c. AC and DD1 are perpendicular; d. BD and CC1 are perpendicular. 4. Let ABCM be a regular triangular pyramid. Prove that: a. AB and CM are skew lines; not paraller, not in the same plane b. BC and AM are skew lines; c. AC and BM are skew lines. 5. Let ABCDM be a regular quadrilateral pyramid. Find the angle between: a. AB and CM; b. BC and DM; c. CD and BM; d. AD and CM. the angle between 4a) M Prove that 2)a) +(AB and .DD. ) = 30 Since they Belong to AB and Close skew lines DO. E ADD. A, , and two plans that AB E ABCD AB.L.DD. are parallel the angle AB E plane ABC = AB and MC Getween AD.D, A. LABCD them 's MC G plane BCM ) ase noncoplanar and ABY C two sufficient conditions le ) BC and CD,, so + (BC and CA )- 90 to say AB and CM ase snew lines 2 1 - 11 5 a) M $ DCM- Prove that AB from ABCP square => all sides ase equal 3 al and CD. ase 4 DCM - equilateral pasquier AB'LIC C PCIIDG ABIGD, ABU PC DADCM =60 - (C) Ac and DD , ase 1 AC= ABCD DP = APD , A ACLDO ABCD LADDA