Given that y = tan²x, show that dy/dx = 2 tan x + 2 tan³ x.
- (a)Given that y = tan²x, show that dy/dx = 2 tan x + 2 tan³ x.[2]
- (b)Find the exact value of ∫(from π/6 to π/3) (tan x + tan²x + tan³x) dx.[6]
Mark scheme
Marking points from the official mark scheme (Feb/Mar 2022). The mark or mark type is shown in brackets.
- [B1] Differentiate to obtain 2 tan x sec² x
- [B1] Use sec² x = 1 + tan² x to confirm 2 tan x + 2 tan³ x [AG – necessary detail needed]
- [M1] Attempt to use part (a) result to integrate tan x + tan³ x
- [A1] Obtain (1/2) tan² x
- [M1] Use relevant identity to integrate tan² x
- [A1] Obtain sec² x - 1 and hence tan x - x
- [M1] Use limits correctly for integrand of form k₁ tan² x + k₂ tan x + k₃x
- [A1] Obtain √3 - π/12 [Or exact equivalent]
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