Answer:
Step-by-step explanation: the best way to get this answer is by using a scientific calculator fx-991es plus I recommend
Let's go manual for now.
Let's covert pi/4 to angle
1⁰ =π/180
1 radian =180/π
Therefore π/4 × 180/π
∅ =45⁰
Sin-¹(tan 45⁰)
Tan 45⁰= 1
Sin-¹ (1) = 90⁰. Press { sin,-¹ (1) } on your calculator
Sin-¹ (tan pi/4) = 90⁰