X/4 = -9
x/4 = -9/1
cross multiply
x = -36
We can calculate using cosinus method in triangle
c² = a² + b² - 2ab cos c
Plug in the number to the formula
c² = a² + b² - 2ab cos c
c² = 10² + 8² - 2(10)(8) cos 105°
c² = 100 + 64 - 160 cos 105°
c² = 164 - 160 (-0.26)
c² = 164 + 41.6
c² = 205.6
c = √205.6
c =14.34
C is 14.34 unit length
Answer:
<em>A.</em>
<em>The student made an error in step 3 because a is positive in Quadrant IV; therefore, </em>
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Step-by-step explanation:
Given



Required
Where and which error did the student make
Given that the angle is in the 4th quadrant;
The value of r is positive, a is positive but b is negative;
Hence;

Since a belongs to the x axis and b belongs to the y axis;
is calculated as thus

Substitute 


Rationalize the denominator


So, from the list of given options;
<em>The student's mistake is that a is positive in quadrant iv and his error is in step 3</em>
Evaluating the tangent function for the two values we obtain the following:
tan 135=tan(135+180)=tan 315=-1
next:
tan -135=tan(180-135)=tan 45=1
thus comparing the two we see that tan 135 is negative while tan -135 is positive