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C2 Trig

If tan theta = 1 and theta is acute, find the exact values of:
sin theta/cos theta.

I understand that I need to make a right angled triangle with opp =1/adj = 1 and hyp = root 2. But what does the question imply by stating that the angle is acute? If another question says the angle is obtuse what does it mean? I know that theta would be in the range 0 < x < 90 and 90 < x < 180.

Has it got to do with which angle to use when drawing the triangle?

Reply 1

BabyMaths

tan(45)=1
tan(225)=1

Which one do you want? :smile:

Reply 2

UKBrah

Original post by BabyMaths

tan(45)=1
tan(225)=1

Which one do you want? :smile:

ohh haha, i was overthinking this. cheers

If sin theta is 5/13, and theta is obtuse, find the exact values of cos theta/tan theta.

I got theta = 22.6 and the other value is 157.4 . But how can I make a right angled triangle with an angle of 157.4?

Reply 3

BabyMaths

Original post by UKBrah

The first diagram here might help.

Reply 4

BabyMaths

together with this

c2 trig.png

Reply 5

UKBrah

Original post by BabyMaths

together with this

c2 trig.png

I get cos x = 12/13 and tan x = 5/12.
The answers are negative tho, is this because both x co-ordinates are negative in the quadrant in which the triangle is in?

c2%20trig.png13.1KB

Reply 6

BabyMaths

Original post by UKBrah

I get cos x = 12/13 and tan x = 5/12.
The answers are negative tho, is this because both x co-ordinates are negative in the quadrant in which the triangle is in?

You should have -12 rather than 12 in the diagram and then you have

tan (157.38..)= 5/-12= - 5/12

and

cos(157.38..)= -12/13.

or if I actually read your question..yes that's right. :wink:

(edited 11 years ago)

Reply 7

UKBrah

Original post by BabyMaths

You should have -12 rather than 12 in the diagram negative and then you have

tan (157.38..)= 5/-12= - 5/12

and

cos(157.38..)= -12/13.

or if I actually read your question..yes that's right. :wink:

how can distance be negative? :confused: