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0 notes &

Can you help me with these trig questions please? :)

1. What is the sector formed by the angle of 240 degrees in a circle with a radius of 5?

(That’s all it says so I’m going to assume that it was asking for the area)

This is my answer: 52.36 square units ( is that correct?).

2. 1/cos(40deg) tan(50deg) - sec(50deg)

I know the answer is 0, but why is it 0?

and

3. why does sin(50deg)/cos(40deg)=1? 



1.area f sector is (area of circle with radius r) * (x/360) x is the angle of the sector, if you did this, your answer is correct


2. 

( tan50)(1/cos40 ) -sec50

= (tan50)(1/sin50) - sec50………………….. nw you would see how it is 0„„„„„, since cos40 = cos(90-50) = sin50 since cos(90-x) = sin x

3 sin 90-x = cosx

so sin 50 = sin(90-40) = cos 40

so cos 40/cos 40 = 1!!

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Determine the exact value of the expression:

I guess my teacher gave us this exercise without teaching us, so can you do all the steps please?

what is tg7pi/6

ok, it is tan 

the chart/table that I made is to show that

there are four quadrants in cartesian plane

first quadrant is from o to pi/2 or from 0 to 90degree

second quadrant is from pi/2 to pi, i.e. from 90 to 180 degrees

third quadrant is from pi to 3pi/2 i.e from 180 to 270 degrees,

and fourth quadrant is from 3pi/2 to 2pi, ie from 270 degrees to 360 degrees

now all trigonometric ratios are positive in first quadrant

only sin is positive in second quadrant, and no other tri ratio is positive in second quadrant, meaning, sin of any angle that lies between 90 and 180 degres is positive,

likewise, for all other quadrants and their respective trig ratio which is positive is written in the chart/table

now 5pi/6 = pi - pi/6

and cos(180-x) = -cosx

sin(180-x) - sinx

thats it

any more queries, feel free to ask

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4 notes &

Disco Kitchen: Trigonometry

lady-swillmart:

Anyone want to help with a math problem?

I have:

(5/7 sin⁴ x) - (10/7 sin² x) + (5/7)

I know the answer is (5/7 cos⁴ x) but I can’t fully work out how or why. I know it involves factoring and fundamental identities and all that jazz.

This type of problem (or anything remotely resembling it) is…

http://askmemathsquestions.tumblr.com/post/32670624707

here is your solution

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5 notes &

Can anyone help me with this problem.

tirrivee:

askmemathsquestions:

tirrivee:

And help me figure through why it’s wrong. Because it is wrong. I have no idea how, though. 

This is my work through it. All I was given were the values in red, aka C = 52 degrees, a = 51, and b = 17.

Pleeease okay thank.

I can help,but it is not legible, can you post a clear pic?

Hopefully this is better? Thank you!

buddy, it is not wrong, 

it is just a part of sin that we( yes, I also overlooked it and ended up wondering that why it is wrong) overlooked.

It got to me when I was thinking that the sum of two sides of a triangle is always greater than the third side.

so the sides satisfied the criteria, I checked it.

the problem was with angles.

then I thought that sin (180-x) = sin x

so one of the angles that we calculated was actually not the answer, we needed to find 180 - x of that angle because sine rule which was used for calculation of the angles dosen’t tells us if the angle we calculated is x or 180-x

because sin x = sin (180-x)

meaning that we could work out 60 degrees, but the angle could have  been 120 degrees.

so which angle was the culprit here?

All we know is that sine rule is mathematical representation of 

the side opposite to the greater angle is the greatest

so, it had to be angle A, which we calculated as 70.28

it is actually, (180-70.28 )

you get this angle, 

and then when you add up angle C and Angle B, you will get 180 degrees

confirm by cosine rule that (180-70.28) is the correct angle A

And thanks for putting this up, I have a exam tomorow and I just got reminded not to blindly mark the answer once we get it, we should check the validity of our results too

see, how just a tiny detail overlooked and WE ended up wondering why the angles won’t add up.

Thanks for putting this up, you really don’t know, you have just helped me for my exam tomorrow


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