Find the magnitude and direction angle of the vector (-2,5). Round to tenths

Question

Find the magnitude and direction angle of the vector (-2,5).  Round to tenths

amistre64 · Answer

square, add, sqrt .... usual distance process

amistre64 · Answer

and since this is in quadrant the arctan will represent in quadrant 4 so adjust by adding pi

amistre64 · Answer

*since its in quadrant 2 ... i said it in my head, but my fingers refused to type it :)

amistre64 · Answer

or just do arccos of x/r

terenzreignz · Answer

If we're arc-ing anyway, might as well just take the arctan of y/x ...

amistre64 · Answer

thats what i normally do, but that only pops out q1 or q4 results

terenzreignz · Answer

oh... right -.-

amistre64 · Answer

if arctan pops out say:  -85, then adding 180 will put it into q2

if it pops out a radian measure, adding pi will accomplish the same thing

but since we can determine r, arccos will give it without any adjustments required

terenzreignz · Answer

You had me at "that's what I normally do, but"
XD