A level maths help

Given that angle B is reflex and tan B= root21 divide by 2, find the exact value of Sin B and cos b.

I understand when the given is sin or cos not tan

Reply 1

Muttley79

Original post

by Toomanyenny

Given that angle B is reflex and tan B= root21 divide by 2, find the exact value of Sin B and cos b.
I understand when the given is sin or cos not tan

What have you tried? If tan is +ve and reflex which quadrant is it in?

Reply 2

Toomanyenny

Original post

by Muttley79

What have you tried? If tan is +ve and reflex which quadrant is it in?

Reflex angle is 3rd or 4th but because tan is positive then 3rd. Other than doing tan^-1(root 21/2) which is 66.42182152 I don’t know what to do

Reply 3

Muttley79

Original post

by Toomanyenny

Reflex angle is 3rd or 4th but because tan is positive then 3rd. Other than doing tan^-1(root 21/2) which is 66.42182152 I don’t know what to do

What trig relationships do you know? Maybe look at those derived from sin^2 x + cos^2 x = 1

Reply 4

Toomanyenny

Original post

by Muttley79

What trig relationships do you know? Maybe look at those derived from sin^2 x + cos^2 x = 1

I really don’t know

Reply 5

Muttley79

Original post

by Toomanyenny

I really don’t know

Maybe look them up as you need a way of finding sin and cos from tan.

Reply 6

davros

Original post

by Toomanyenny

I really don’t know

If you know that basic identity, what can you divide both sides by to get an identity that involves tan^2 x ?

Reply 7

Hugfhsvh

Original post

by Toomanyenny

Given that angle B is reflex and tan B= root21 divide by 2, find the exact value of Sin B and cos b.
I understand when the given is sin or cos not tan

Maybe try dividing it by a trigonometric function such that you get an identity relating secant squared and tangent squared...?

Reply 8

Hugfhsvh

There are ways of finding sin and cos from tan by just using the sin² and cos² identity without expressing the identity using tan²

(edited 1 month ago)

Reply 9

ClarinetQueen

TSR Community Staff

Hello all,

I have removed several posts from this thread. As a reminder, please treat each other with respect and courtesy. I would suggest that you also remember that the focus of this thread should remain helping the OP.

Thanks,

CQ