• YOU can help the next generation of students in the community!
    Share your trial papers and notes on our Notes & Resources page

Math year 10 5.3: trigonometric relations (1 Viewer)

jane1820

Well-Known Member
Joined
Jul 15, 2024
Messages
743
Gender
Female
HSC
2026
i dont understand why the questions specify this, if im being honest i dont see any use for it
can someone explain? IMG_9652.jpeg
like i just draw a triangle, choose any side i want (except the right angle side) label the angle as X (for number 5 for example) n since we knew that cosX=2/3 then the hypotenuse is 3 n i work from there literally dont see a use for the X+Y=90 degrees bit
 

WeiWeiMan

Well-Known Member
Joined
Aug 7, 2023
Messages
978
Location
behind you
Gender
Male
HSC
2026
i dont understand why the questions specify this, if im being honest i dont see any use for it
can someone explain? View attachment 44402
like i just draw a triangle, choose any side i want (except the right angle side) label the angle as X (for number 5 for example) n since we knew that cosX=2/3 then the hypotenuse is 3 n i work from there literally dont see a use for the X+Y=90 degrees bit
3) a+b = 90˚ actually defines wtf b is
cos(b) = cos(90˚-a) = sin(a) = 5/13
cos(a) = sqrt(1-sin^2(a)) =12/13 = sin(b)

ngl, reading all the questions, they're just defining what the angles are
 

jane1820

Well-Known Member
Joined
Jul 15, 2024
Messages
743
Gender
Female
HSC
2026
3) a+b = 90˚ actually defines wtf b is
cos(b) = cos(90˚-a) = sin(a) = 5/13
cos(a) = sqrt(1-sin^2(a)) =12/13 = sin(b)

ngl, reading all the questions, they're just defining what the angles are
Yh but i solved the question without referring to that bit if ykwim?
u can see that i solved it (i usually just draft on the textbook before writing the final answer) but i didnt refer to that bit
am i doing the question right through a wrong approach?
like image.jpg
 

WeiWeiMan

Well-Known Member
Joined
Aug 7, 2023
Messages
978
Location
behind you
Gender
Male
HSC
2026
Yh but i solved the question without referring to that bit if ykwim?
u can see that i solved it (i usually just draft on the textbook before writing the final answer) but i didnt refer to that bit
am i doing the question right through a wrong approach?
like View attachment 44403
yeah
if alpha and beta were defined in any other way, your approach wouldn't work. the a+b=90˚ defined them as those other angles in a right angled triangle.
 

Luukas.2

Well-Known Member
Joined
Sep 21, 2023
Messages
459
Gender
Male
HSC
2023
i dont understand why the questions specify this, if im being honest i dont see any use for it
can someone explain? View attachment 44402
like i just draw a triangle, choose any side i want (except the right angle side) label the angle as X (for number 5 for example) n since we knew that cosX=2/3 then the hypotenuse is 3 n i work from there literally dont see a use for the X+Y=90 degrees bit
I am guessing that you are just starting to deal with angles of any magnitude, and thus that trig functions aren't always positive.

In each case, the noted information is meant to tell you that the two angles are both acute and complementary... you need the (highlighted) complementary part to relate results from angle X to angle Y. In other words, knowing that


But, you also need the acute part (or equivalent information) to deduce whether the trig functions are all positive. If both angles aren't acute then there may be two possible answers for some parts as non-acute angles can have trig functions that are negative. In other words,


Your answers are assuming the acute part, which technically isn't justified.











 

jane1820

Well-Known Member
Joined
Jul 15, 2024
Messages
743
Gender
Female
HSC
2026
I am guessing that you are just starting to deal with angles of any magnitude, and thus that trig functions aren't always positive.

In each case, the noted information is meant to tell you that the two angles are both acute and complementary... you need the (highlighted) complementary part to relate results from angle X to angle Y. In other words, knowing that


But, you also need the acute part (or equivalent information) to deduce whether the trig functions are all positive. If both angles aren't acute then there may be two possible answers for some parts as non-acute angles can have trig functions that are negative. In other words,


Your answers are assuming the acute part, which technically isn't justified.











OHHHH OK THX
n yh the next chapter was all abt the negatives n positives so i think that bit was to tell me that they ’wont’ be negative considering i wouldnt have known
anyways thank u
 

Users Who Are Viewing This Thread (Users: 0, Guests: 1)

Top