cotA = tan(90degrees- A) True or False

Question

The vectors <4, 5> and <-10, 8> are orthogonal True or False

2<3, 5> = 16 True or False

<2. 3>*<4, 3> =

<2, 6> + <4, 5> =

Find c if a = 3, b = 5, and A = 30degrees=

Answer 1

the co- in the trig functions means co-mplementary angle.

cos(x) = sin(90-x)
cot(x) = tan(90-x)
csc(x) = sec(90-x)

#2 true. review the dot product.

#3 eh? a vector and a scalar?

#4 2*4 + 3*3
if * means dot product

#5 <2+4,6+5>

for the last one, use the law of sines to find B:
sinB/5 = sin30/3
Now, with B, C=180-(A+B) and using the law of cosines,
c^2 = 3^2+5^2-2*3*5cosC