trig question =] (1 Viewer)

[akukei]

trig question =] - help please!!

Find the values of x which satisfy the equation 5cos(x/2) = -1, in radians to 2dp. -2pi <= x <= 2pi

The given answer is +4.19, -4.19 but i can't get it.

can someone pretty please confirm this/explain?

Edit: I keep getting +/- 3.54

 

[Forbidden.]

Re: trig question =] - help please!!

Find the values of x which satisfy the equation 5cos(x/2) = -1, in radians to 2dp. -2pi <= x <= 2pi

The given answer is +4.19, -4.19 but i can't get it.

can someone pretty please confirm this/explain?

Edit: I keep getting +/- 3.54

You are correct.
I solved this both on paper and using a mathematics software and your answer is definitely the one.

cos(x/2) = - 1/5

x/2 = cos^-1(-1/5)

x = 2 cos^-1(-1/5)
x = 3.544308495 ... (on calculator)

(Software produces: 3.5443084951704548213728944877147497046772455621796 to 50 decimal places)

As my math tutor says .... the answers, well, are correct 95% of the time.

 

[akukei]

thank you

 

[AnandDNA]

what software is it??

 

[Forbidden.]

what software is it??

Maple 11.