What is componendo and dividendo method? Plz explain.

cos20.cos40.cos80=1/8

Prove that.....Tan 70 = tan 20 + 2 tan 50...

Solve Sinx + Sin3x + Sin5x = 0.

sin 20 sin 40 sin 60 sin 80=3/16

solution of ml agarwal for isc 11std

The chapter trigonometry in RS Aggarwal book (of class 11th) is divided into 6 sub-chapters. But its chapter 5 ( Solution of triangles ) and 6 ( Graphs of trigonometric functions ) are not the topics of NCERT Book.

Now my question is: Should I study these two chapters (5 &6 of RS Aggarwal) as these are not in NCERT Book?

prove the following :

root 3 cosec 20 - sec 20 = 4

prove that tan20 .tan40.tan80=tan60.

sin^{4}x+cos^{4}x=1-2sin^{2}xcos^{2}x

cos^{2}x + cos^{2}(x + pi/3) + cos^{2}(x - pi/3) = 3/2. prove

cotx cot2x - cot2x cot3x-cot3x cotx=1

sinA . sin(60-A) . sin(60+A) = 1/4 sin3A

if sin alpha + sin beta= a and cos alpha + cos beta= b, show that

1. Sin(alpha+beta)= 2ab/a sq.+b sq.

2. Cos(alpha+beta)= b sq.-a sq./b sq.+a sq.

What is componendo and dividendo method? Plz explain.

cos20.cos40.cos80=1/8

Prove that.....Tan 70 = tan 20 + 2 tan 50...

Solve Sinx + Sin3x + Sin5x = 0.

sin 20 sin 40 sin 60 sin 80=3/16

solution of ml agarwal for isc 11std

The chapter trigonometry in RS Aggarwal book (of class 11th) is divided into 6 sub-chapters. But its chapter 5 ( Solution of triangles ) and 6 ( Graphs of trigonometric functions ) are not the topics of NCERT Book.

Now my question is:

Should I study these two chapters (5 &6 of RS Aggarwal) as these are not in NCERT Book?prove the following :

root 3 cosec 20 - sec 20 = 4

prove that tan20 .tan40.tan80=tan60.

sin

^{4}x+cos^{4}x=1-2sin^{2}xcos^{2}xcos

^{2}x + cos^{2}(x + pi/3) + cos^{2}(x - pi/3) = 3/2. provecotx cot2x - cot2x cot3x-cot3x cotx=1

sinA . sin(60-A) . sin(60+A) = 1/4 sin3A

if sin alpha + sin beta= a and cos alpha + cos beta= b, show that

1. Sin(alpha+beta)= 2ab/a sq.+b sq.

2. Cos(alpha+beta)= b sq.-a sq./b sq.+a sq.