101,909,111 hcf

some mistake on the question why please manage this mistake 

Integrate cos x / (cos x/2 + sin x/3)^3 0 to pi/2

Ques 6 part i 

Elements of maths

indefinite integral6 

If D is the mid .point of side of side BC of a ΔABC, P and Q are two points lying respectively on the sides AB and BC such that DP is parallel to QA. Prove that ar(ΔCQP) = 1/2 ar(ΔABC).

• Area of elliptical shape who is a=5 and b=3.5 
  

4.2 8th problem solution is wrong its yz-zx

In 11th ncert book ,ex. 10.3 ,  3 q. That is y=0 what is the coeffocient of x and constant c

• A solid right circular cone of diameter 14 can and height 8 cm is melted to form a hollow sphere.If the external diameter of sphere is 10 cm then find it's internal diameter

Is it necessary to do reference books like Rd sharma for exams of class 9th?