sin225 is in the third quadrant, sine is negative.
cos-390 is in the fourth quadrant, positive.
change that sign, you get it (after rationalizing the denominator)
Solve cos315*cos(-390)-sin225*sin750
cos315:
<RA = 360-315
= 45
cos45 = 1/√2
cos-390:
<RA=-390+360
=30
cos30= √3/2
sin225:
<RA = 225-180
= 45
Sin45=1/√2
Sin750:
<RA = 750 - 2(360)
=30
Sin30=1/2
Put it all together...
(1/√2)(√3/2)-(1/√2)(1/2)
=√3/2√2 - 1/2√2
The answer in the back is √2 + √6/4...
What did I do wrong?
2 answers
Thanks^