For cbse physics class 12 the derivations in ncert are in complete

CBSE Class 12
1

For cbse physics class 12 the derivations in ncert are in compelete and are confusing what should be done?

2

For physics class 12 the derivations in ncert,

They are not incomplete. But some steps are missed out.Those you can include, but stick to NCERT derivations as board prefers that.According to CBSE guide line for checking the papers, that derivation is asked.