Question

sir 5.1, 5 question .. 

sir when we subtracting 1from to 

how can come -DC one side and +DC second side.

tell me sir i am not getting... plzzzz

Write (1/3+3i) in the form of a+ib

Sir i didn't understand how can we similarly prove that AB/DE= BC/EF

xcos (a+y)=cosy, Hence prove, y'=cos^2(a+y) / sina

28.5-30=(60-6x) /15

Sir in this question can't we use PE/PQ =PF/FR and why not?

PLEASE clear me with this one