Am I allowed to open these brackets of t the angle?

Question

Sin(X)Cos(90-V)
can it equal to sin(x)(Cos(90)-cos(v))?????????????

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Answer 1 · 2017-11-28T02:59:19

Please see below.

.

I think you want to know if:

#cos(90-v)=cos90-cosv#

The answer is no. There is a formula for this:

#cos(a-b)=cosacosb+sinasinb#

Therefore:

#cos(90-v)=cos90cosv+sin90sinv#

#cos(90-v)=(0)(cosv)+(1)(sinv)=0+sinv#

#cos(90-v)=sinv#