Rbse maths 12th new syllabus

a hemispherical depression is cut out from one face

1. In trapezium abcd ab||cd,<a=(2x-35)<b=y,<c=85  and<d=(3x+65) find the value of x and y

please help me

The perpendicular distance of the line from the origin is 5cm and its slope is -1 find the equation of the line 

Sir can you explain what is the difference between parallelogram and quadrilateral 

• Solve by elimination method 
• ax/b-by/a=a+b
• ax-by=2

Why didn't we integrate (cos 2x)square which is of the form x to the power n as x to the power n+1/n+1 in Q10 ex7.3

Sir regarding the problem 9th class maths  ex-9.2(1) . Considering the diagram the final solution is that AD=12.48 . But while considering only right triangle CDF and solving for DF =√DC^2-CF^2  i get DF = 12.48 . How come it's possible ???