Question

Trig help please Find the exact value of each trigonometric equation

Answer 1

The exact value for the equation is true but I don't really think that's the question so anyways...

- 15.) The exact form for this equation is -13pi/3 and the decimal form -13.613...

- 16.) The exact form for this equation is 23pi/4 and the decimal form 18/064...

- 17.) The exact form is -7pi/2 as the decimal is -10.995...

- 18.) The exact is -29pi/6 and the decimal is -15.184...

Answer 2

We know any trig problem that asks for exact values probably has something to do with 30° or 45° and their multiples.  That's $\pi/6$ and $\pi/4$; we're apparently doing radians in this one.

General rules off the top of my head: Coterminal angles (gotten by adding or subtracting multiples of 2π) have the same values for their trig functions , cosine is even, sine is odd, cosine negate supplementary angles, sine of supplementary angles is unchanged, and the cosine of an angle is the sine of the complementary angle.

15

$\cos (- \frac{13\pi}{3}) = \cos( 13\pi/3-6(2\pi)) =\cos(\pi/3) = \frac 1 2$

16

$\csc(\frac{23 \pi}{4}) = \dfrac{1}{\sin (23\pi/4 - 3(8\pi/4))} = \dfrac{1}{\sin(-\pi/4)}= \dfrac{1}{- 1 /\sqrt{2}} = - \sqrt{2}$

17

$\sec(-\frac {7 \pi}{2}) = \dfrac{1}{\cos(-7\pi/2+ (4/2)(2\pi) )}= \dfrac{1}{\cos(\pi/2)} = \dfrac 1 0$

That one is undefined

18

$\cot(-\frac{29\pi}{6}) = \cot(-29\pi/6 + (18/6) (2 \pi)) = \cot(7\pi/6) \\= \tan(\pi/2 - 7\pi/6) = \tan(-4\pi/6)= \tan(-2\pi/3 + \pi) = \tan(\pi/3)= \sqrt{3}$

Whoever created this math homework problem needs a lesson in writing and typesetting math.  Let's list the errors:

Exact -- capitalized

each equation -- there are no equations

0 to 2 pi for theta -- do they want us to find the values or find the thetas but not evaluate the trig function?

theta is spelled out, not typeset

trig functions shouldn't be typeset in italics

sec -(7 pi/2)  is a typo

Sometimes there's a space after the problem number sometimes there isn't

This is awful.  Demand more of your teachers and online exercises!