Tangent of 2 times arc cosine of -3/4

Asked Oct 06 '15 at 04:35

Active Oct 06 '15 at 04:35

Viewed 61 times

Tan[ArcCos[-3/4]

Returns the exact answer:

-(Sqrt[7]/3)

But:

Tan[2 ArcCos[-3/4]]

Does not return an exact answer. Any way to force it to return an exact answer?

asked Oct 06 '15 at 04:35

David

3

Tan[2 ArcCos[-3/4]] // FunctionExpand returns -3*Sqrt[7] – Bob Hanlon Oct 06 '15 at 04:42
2

Or Tan[2 ArcCos[-3/4]] // TrigToExp // FullSimplify – Bob Hanlon Oct 06 '15 at 04:51
@BobHanlon Awesome, so helpful for tomorrow's class. Thanks. – David Oct 06 '15 at 04:55

0 Answers0