Solve #cos(-60^o)-tan135^o-:tan315^o +cos660^o#?

1 Answer
Shwetank Mauria
Jul 3, 2016

#cos(-60^o)-tan135^o-:tan315^o +cos660^o=0#

Explanation:

To solve #cos(-60^o)-tan135^o-:tan315^o +cos660^o#

we make use of #cos60^o=1/2# and #tan45^o=1# and also the identities #cos(-A)=cosA# and #tan(360^o-A)=tan(180^o-A)=-tanA#.

Hence #cos(-60^o)-tan135^o-:tan315^o +cos660^o#

= #cos60^o-tan(180^o-45^o)-:tan(360^o-45^o) +cos(720^o-60^o)#

= #cos60^o-(-tan45^o)-:(-tan45^o) +cos(-60^o)#

= #1/2-(-1)-:(-1) +cos60^o#

= #1/2-1+1/2=0#

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