Question

what is cot2a=0 Thus 2a=90˚....how did this happen?

Answer 1

\[ cot2a = 0 => \frac{cos2a}{sin2a} = 0 => cos2a = 0 => 2a = cos(0)\]

Answer 2

wait i made a typo:
\[ 2a = cos^{-1}(0)\]

Answer 3

since you know that \(cos^{-1}(0) = 90\)

Answer 4

then \( 2a = 90\)

Answer 5

wait how did cot2a= cos2a/sin2a?

Answer 6

Firstly you should remember that:
\[\cos(90) = 0\]

Answer 7

because \[ cota = \frac{cosa}{sina}\]

Answer 8

*cot

Answer 9

\[\large \cot(90^{\circ}) = 0\]

Answer 10

So you can replace 0 with cot(90):

\[\cot(2a) = \cot(90)\]

Answer 11

im sorry but isnt cot= 1/tana?

Answer 12

well you can use that method if you remember whats cot(90)

Answer 13

Now as trigonometric ratio is same:

So you can equate the angles:

\[2a = 90\]

Answer 14

yes it because what tana?

Answer 15

what is*

Answer 16

yes it is but whats tan(a) then?*

Answer 17

oh cot also equals to x/y so cos/sin right??

Answer 18

Right..

Answer 19

ohhhh okay it makes sense

Answer 20

so i get that cos2a/sin2a = 0 but then what is next?

Answer 21

i typed the solution for you already..

Answer 22

Multiply by sin(2a) both the sides..

Answer 23

so it becomes cos2a (sin2a) = 0 (sin2a)

Answer 24

No..

There is one sin(2a) in the denominator too..

Answer 25

Can't you cancel sin(2a) with sin(2a) on left hand side ??

Answer 26

so does it become like this?

Answer 27

Yep..

Answer 28

oh okay now i get the steps! thank you so much @waterineyes @Mimi_x3

Answer 29

Welcome dear..