Question

***Help for a medal and fan!***

Write the following expression as a function of a positive acute angle.

cos 125°

a)cos55°
b)-cos55°
c)cos(-55)°

Answer 1

\[\cos(180-\theta)=-\cos(\theta)\]

Answer 2

cos(180-125)=-cos(55)

Answer 3

so in my calculator I just type in cos(180-125) then will that give me my answer? can you explain please? @nitz

Answer 4

u dont need a calculator

Answer 5

The acute angle is the small angle which is less than 90°.

Answer 6

ok... so i just subtract ? and how will i know if the cos is negative or not

Answer 7

to convert the expression........
\[\cos(180-\theta)=-\cos(\theta)\]

Answer 8

\[\cos(\theta) \] is negaTIVE IN SECOND QUADRANT....

Answer 9

and \[(180-\theta)\] is the angle in second quadrant

Answer 10

okay i get it.... thanks for your help!!!

Answer 11

<90 first quadrant
\[90<\theta<180\] 2nd quadrant
\[180<\theta<270\] third quadrant
\[270<\theta<360 \] fourth quadrant

Answer 12

cos is negative in second and third quadrant....

Answer 13

thanks! :)