Friday

April 18, 2014

April 18, 2014

Posted by **Claire** on Saturday, August 7, 2010 at 4:21am.

a. 1/2

b. ð /6

c. -1/2

d. - ð /6

8. Evaluate cos[tan^-1(5/12)].

a. 12/13

b. 12/5

c. 5/12

d. 5/13

9. Evaluate cos[sin^-1(-3/5)].

a. -4/5

b. 5/4

c. 4/5

d. -3/4

- Inverse Functions & Trig. Equations -
**Reiny**, Saturday, August 7, 2010 at 9:01amI don't know at what level you have studied inverse trig functions, but Sal Khan has hundreds of very simple videos on Youtube.

http://www.youtube.com/watch?v=JGU74wbZMLg

Let's look at your #9

first of all sin^-1 (-3/5) to me means ..

give me the angle Ø so that sinØ = -3/5

and since sin (of angle) = opposite/hypotenuse, I see the famous 3-4-5 triangle.

But since the sine is negative, I could sketch that triangle in quadrants III or IV,

(I will pick IV since -Ø is the smallest angle)

so now we want

cos(the angle of that triangle) = adj/hyp = 4/5

Of course you could just blindly let your calculator do the work for you ...

on mine :

2nd F

sin

(-3/5)

=

cos

=

and I got 0.8 which is 4/5

Now do #2 the same way.

BTW, wouldn't #1 be -1/2 by the

"Just look at it" Theorem ?

**Related Questions**

Math - Evaluate *Note - We have to find the exact value of these. That I know to...

trig - hoW to evaluate these if cos=-12/13, A in Q II and cot B =5/12, B in Q ...

Trig - Given: cos u = 3/5; 0 < u < pi/2 cos v = 5/13; 3pi/2 < v < ...

Inverse trigonometric function - How to solve without calculator 1. sin(arctan(...

math - tan (u-v) given sin u=3/4 and cos v= -5/13 with U and V in quadrant 2 Use...

Math - please help - If x and y are in the interval (0,π/12) and sin x = 3/...

Math help please - If x and y are in the interval (0,π/12) and sin x = 3/5 ...

Trigonometry - Use the trig Identities to find the other 5 trig functions. ...

Math - 3. find the four angles that define the fourth root of z1=1+ sqrt3*i z...

trig - suppose sin(x)=4/5 and cos(y)=-12/13, and x and y are in the second ...