Thread: trigonometry

hi!
Can someone teach me how to solce arccos(cos(7Pi/ 6))?

i tried to change 7pi/ 6 into the principal angle but what i thought of was:

cos (7pi/6)= -cos (pi/6)

although it is in the principal angle, i do not know how to continue after that.

thanks!

Originally Posted by alexandrabel90

hi!
Can someone teach me how to solce arccos(cos(7Pi/ 6))?

i tried to change 7pi/ 6 into the principal angle but what i thought of was:

cos (7pi/6)= -cos (pi/6)

although it is in the principal angle, i do not know how to continue after that.

thanks!

HI

it would be

cos (7pi/6)= -cos (pi/6)=cos (5pi/6)

Lets say





So now , cancel the 'cos' , thus

Note that its different when its something

but i thought that way that you did only applies to when the angle is in the principal range of 0 to 180 degrees?

so i was trying to convert 7pi/6 into the principal angle of cos x where x is in the principal range so that i can use the method that you have just used..

Originally Posted by alexandrabel90

but i thought that way that you did only applies to when the angle is in the principal range of 0 to 180 degrees?

so i was trying to convert 7pi/6 into the principal angle of cos x where x is in the principal range so that i can use the method that you have just used..

yeah you are right , i just edited .