misc trignometric questions (1 Viewer)

[darshil]

hey everyone,
just have trouble with these two questions:

1) Find equivalent expression of cos (3pi/2+x)
2) how do I go about graphing (sin^2x) ?

 

[me dumb]

hey everyone,

2) how do I go about graphing (sin^2x) ?

if u want u could whack some numbers into ur calc and plot pts

 

[gurmies]

Okay, cos(3pi/2+x) = cos(3pi/2)cosx - sin(3pi/2)sinx = sinx...Sketching sin^2x will look like sinx however range is 0 to 1 and the negative parts are reflected up. At places where it cuts the x-axis, it will become a stationary point.

EDITED: ignore error

 

[ninetypercent]

when Asin^nx
A is the amplitude
range is 2pi/n

sketching sin^2x
range is 2pi/n => range is pi
amplitude is 1
absolute value => reflect the negative bits via the x axis

 

[Timothy.Siu]

Okay, cos(3pi/2+x) = cos(3pi/2)cosx - sin(3pi/2)cosx = cosx...since you don't do extension maths, think about it as 270 + an angle (assuming acute) will end up in the 4th quadrant, which just means cosx

Sketching sin^2x will look like sinx however range is 0 to 1 and the negative parts are reflected up. At places where it cuts the x-axis, it will become a stationary point.

thats wrong, and thats a bad way to do it.

cos(3pi/2+x)=cos(2pi-(3pi/2+x))=cos(pi/2-x)=sinx

 

[gurmies]

thats wrong, and thats a bad way to do it.

cos(3pi/2+x)=cos(2pi-(3pi/2+x))=cos(pi/2-x)=sinx

How come it's a bad way? I made a mistake with the formula, however it does yield the correct answer...

 

[Timothy.Siu]

How come it's a bad way? I made a mistake with the formula, however it does yield the correct answer...

exactly, its easier to make a mistake and its slower, and its also not a 2unit method.

 

[gurmies]

Ah, point noted. I wouldn't say slower though...

 

[Timothy.Siu]

Ah, point noted. I wouldn't say slower though...

its more thinking at least

 

[darshil]

thank you for all the help everyone

 

[untouchablecuz]

its more thinking at least

o noez

 

[Revacious]

sub random values of x into your calculator, till it works out. That's the next best way.

 

[Uncle]

sub random values of x into your calculator, till it works out. That's the next best way.

kind of dodgy approach though,
this is only allowed in university where i used a mathematical computing program (like MAPLE) and generated a table of values for sin(x) where x is an integer from 1 to 100